Significant Figures Practice Worksheet - Free Printable
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Step-by-step solution for: Significant Figures Practice Worksheet
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Show Answer Key & Explanations
Step-by-step solution for: Significant Figures Practice Worksheet
Let’s go through each element one by one and find how many valence electrons it has.
Remember: Valence electrons are the electrons in the outermost shell (highest principal energy level). For most elements, we look at the s and p orbitals of that outermost level. Transition metals (like iron, zinc, copper) can be tricky — but for this worksheet, we’ll follow the simple rule: count only the electrons in the highest n-level s and p orbitals. If there’s no p orbital in the outermost level, just count the s electrons.
We’ll use the periodic table groups to help:
- Group 1 → 1 valence electron
- Group 2 → 2 valence electrons
- Groups 13–18 → subtract 10 from group number (e.g., Group 17 → 7 valence electrons)
- Helium is special: it’s in Group 18 but only has 2 valence electrons (since its outer shell is 1s²)
- For transition metals (Groups 3–12), we usually say they have 2 valence electrons (from the s orbital of the outermost shell), unless specified otherwise. But note: some worksheets treat them differently — here, since the example uses carbon (main group), and the instructions say “always ‘s’ or ‘s and p’”, we’ll stick to counting only the outermost s and p electrons.
Let’s do each:
1. Fluorine (F) – Group 17 → 7 valence electrons
Configuration: 1s² 2s² 2p⁵ → outermost is n=2: 2+5 = 7
2. Phosphorus (P) – Group 15 → 5 valence electrons
Configuration: [Ne] 3s² 3p³ → 2+3 = 5
3. Calcium (Ca) – Group 2 → 2 valence electrons
Configuration: [Ar] 4s² → 2
4. Nitrogen (N) – Group 15 → 5 valence electrons
Configuration: 1s² 2s² 2p³ → 2+3 = 5
5. Iron (Fe) – Transition metal. Outermost shell is 4s². No 4p electrons. So 2 valence electrons.
(Note: Some might argue about d electrons, but per worksheet rules — only s and p in outermost level → so 2)
6. Argon (Ar) – Group 18 → 8 valence electrons
Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ → outermost n=3: 2+6 = 8
7. Potassium (K) – Group 1 → 1 valence electron
Configuration: [Ar] 4s¹ → 1
8. Helium (He) – Group 18, but only 1s² → 2 valence electrons (special case)
9. Magnesium (Mg) – Group 2 → 2 valence electrons
Configuration: [Ne] 3s² → 2
10. Sulfur (S) – Group 16 → 6 valence electrons
Configuration: [Ne] 3s² 3p⁴ → 2+4 = 6
11. Lithium (Li) – Group 1 → 1 valence electron
Configuration: 1s² 2s¹ → 1
12. Zinc (Zn) – Transition metal. Outermost shell is 4s². No 4p. So 2 valence electrons.
(Configuration: [Ar] 3d¹⁰ 4s² → outermost n=4: only 4s² → 2)
13. Carbon (C) – Given in example → 4 valence electrons
14. Iodine (I) – Group 17 → 7 valence electrons
Configuration: [Kr] 5s² 4d¹⁰ 5p⁵ → outermost n=5: 2+5 = 7
15. Oxygen (O) – Group 16 → 6 valence electrons
Configuration: 1s² 2s² 2p⁴ → 2+4 = 6
16. Barium (Ba) – Group 2 → 2 valence electrons
Configuration: [Xe] 6s² → 2
17. Aluminum (Al) – Group 13 → 3 valence electrons
Configuration: [Ne] 3s² 3p¹ → 2+1 = 3
18. Hydrogen (H) – Group 1 → 1 valence electron
Configuration: 1s¹ → 1
19. Xenon (Xe) – Group 18 → 8 valence electrons
Configuration: [Kr] 5s² 4d¹⁰ 5p⁶ → outermost n=5: 2+6 = 8
20. Copper (Cu) – Transition metal. Outermost shell is 4s¹ (note: exception configuration). So 1 valence electron? Wait — let’s check.
Actually, copper’s electron configuration is [Ar] 3d¹⁰ 4s¹. So outermost level is n=4, which has only 4s¹ → so 1 valence electron? But wait — many sources say copper has 1 or 2 valence electrons depending on context. However, per the worksheet’s rule: “valence electrons are the electrons in the outermost principal energy level” and “always ‘s’ or ‘s and p’”. Since copper’s outermost level (n=4) has only 4s¹, that’s 1 electron.
BUT — hold on! In many high school contexts, especially with transition metals, they often say “transition metals have 2 valence electrons” because they lose the s electrons first. However, copper is an exception — it’s 4s¹ 3d¹⁰, so technically only 1 in the outermost s orbital.
However, looking back at the worksheet’s example and instructions — it says “they are always ‘s’ or ‘s and p’ electrons”. So for copper, outermost level is n=4, which has only 4s¹ → so 1 valence electron.
But let me double-check common teaching practice: Many textbooks list copper as having 1 or 2 valence electrons. To be safe, let’s see what the pattern is.
Wait — actually, in the periodic table, copper is in Group 11. For main group, Group 11 would be... but it’s transition. The safest way for this worksheet: since the instruction says “outermost principal energy level”, and for Cu it’s 4s¹, then answer is 1.
However, I recall that sometimes copper is considered to have 2 valence electrons because it can form +2 ions. But strictly by definition given: outermost level electrons in s and p orbitals → 4s¹ → 1.
But let me verify with a reliable source mentally: Standard answer for copper in such worksheets is often 1 or 2? Actually, upon second thought — many curricula teach that all transition metals have 2 valence electrons (the ns²), even if exceptions like Cr and Cu exist. But Cu is 4s¹, so it should be 1.
To resolve this: Let’s look at zinc — it’s 4s², so 2. Copper is before zinc, and it’s 4s¹, so 1.
I think for accuracy, we’ll go with 1 for copper.
But wait — let’s check online or standard knowledge: Actually, in many high school chemistry classes, when asked for valence electrons of transition metals without specification, they expect 2. But the worksheet defines it clearly: “electrons in the outermost principal energy level” and “always ‘s’ or ‘s and p’”.
For copper: outermost principal energy level is n=4. Electrons in n=4: only 4s¹ → so 1.
Similarly, chromium is 4s¹ 3d⁵ → 1 valence electron by this definition.
So I’ll go with 1 for copper.
But let me confirm with another approach: The maximum number of valence electrons is 8, and for transition metals, we don’t count d electrons as valence in this context.
Yes, so:
Final answers:
1. fluorine: 7
2. phosphorus: 5
3. calcium: 2
4. nitrogen: 5
5. iron: 2 (outermost 4s²)
6. argon: 8
7. potassium: 1
8. helium: 2
9. magnesium: 2
10. sulfur: 6
11. lithium: 1
12. zinc: 2 (4s²)
13. carbon: 4
14. iodine: 7
15. oxygen: 6
16. barium: 2
17. aluminum: 3
18. hydrogen: 1
19. xenon: 8
20. copper: 1 (4s¹)
Wait — I’m now doubting copper. Let me think again.
In many standardized tests and worksheets, copper is listed as having 1 valence electron because of its configuration. For example, in AP Chemistry, they consider the 4s electron as valence.
Yes, I think 1 is correct.
But to be absolutely sure, let's see: The worksheet says "the valence electrons are the electrons in the outermost principal energy level". For copper, atomic number 29: 1s2 2s2 2p6 3s2 3p6 4s1 3d10. The outermost principal energy level is n=4, which contains only the 4s1 electron. So yes, 1 valence electron.
Okay, final list:
1. 7
2. 5
3. 2
4. 5
5. 2
6. 8
7. 1
8. 2
9. 2
10. 6
11. 1
12. 2
13. 4
14. 7
15. 6
16. 2
17. 3
18. 1
19. 8
20. 1
I think that's accurate based on the definition given.
Final Answer:
1. 7
2. 5
3. 2
4. 5
5. 2
6. 8
7. 1
8. 2
9. 2
10. 6
11. 1
12. 2
13. 4
14. 7
15. 6
16. 2
17. 3
18. 1
19. 8
20. 1
Remember: Valence electrons are the electrons in the outermost shell (highest principal energy level). For most elements, we look at the s and p orbitals of that outermost level. Transition metals (like iron, zinc, copper) can be tricky — but for this worksheet, we’ll follow the simple rule: count only the electrons in the highest n-level s and p orbitals. If there’s no p orbital in the outermost level, just count the s electrons.
We’ll use the periodic table groups to help:
- Group 1 → 1 valence electron
- Group 2 → 2 valence electrons
- Groups 13–18 → subtract 10 from group number (e.g., Group 17 → 7 valence electrons)
- Helium is special: it’s in Group 18 but only has 2 valence electrons (since its outer shell is 1s²)
- For transition metals (Groups 3–12), we usually say they have 2 valence electrons (from the s orbital of the outermost shell), unless specified otherwise. But note: some worksheets treat them differently — here, since the example uses carbon (main group), and the instructions say “always ‘s’ or ‘s and p’”, we’ll stick to counting only the outermost s and p electrons.
Let’s do each:
1. Fluorine (F) – Group 17 → 7 valence electrons
Configuration: 1s² 2s² 2p⁵ → outermost is n=2: 2+5 = 7
2. Phosphorus (P) – Group 15 → 5 valence electrons
Configuration: [Ne] 3s² 3p³ → 2+3 = 5
3. Calcium (Ca) – Group 2 → 2 valence electrons
Configuration: [Ar] 4s² → 2
4. Nitrogen (N) – Group 15 → 5 valence electrons
Configuration: 1s² 2s² 2p³ → 2+3 = 5
5. Iron (Fe) – Transition metal. Outermost shell is 4s². No 4p electrons. So 2 valence electrons.
(Note: Some might argue about d electrons, but per worksheet rules — only s and p in outermost level → so 2)
6. Argon (Ar) – Group 18 → 8 valence electrons
Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ → outermost n=3: 2+6 = 8
7. Potassium (K) – Group 1 → 1 valence electron
Configuration: [Ar] 4s¹ → 1
8. Helium (He) – Group 18, but only 1s² → 2 valence electrons (special case)
9. Magnesium (Mg) – Group 2 → 2 valence electrons
Configuration: [Ne] 3s² → 2
10. Sulfur (S) – Group 16 → 6 valence electrons
Configuration: [Ne] 3s² 3p⁴ → 2+4 = 6
11. Lithium (Li) – Group 1 → 1 valence electron
Configuration: 1s² 2s¹ → 1
12. Zinc (Zn) – Transition metal. Outermost shell is 4s². No 4p. So 2 valence electrons.
(Configuration: [Ar] 3d¹⁰ 4s² → outermost n=4: only 4s² → 2)
13. Carbon (C) – Given in example → 4 valence electrons
14. Iodine (I) – Group 17 → 7 valence electrons
Configuration: [Kr] 5s² 4d¹⁰ 5p⁵ → outermost n=5: 2+5 = 7
15. Oxygen (O) – Group 16 → 6 valence electrons
Configuration: 1s² 2s² 2p⁴ → 2+4 = 6
16. Barium (Ba) – Group 2 → 2 valence electrons
Configuration: [Xe] 6s² → 2
17. Aluminum (Al) – Group 13 → 3 valence electrons
Configuration: [Ne] 3s² 3p¹ → 2+1 = 3
18. Hydrogen (H) – Group 1 → 1 valence electron
Configuration: 1s¹ → 1
19. Xenon (Xe) – Group 18 → 8 valence electrons
Configuration: [Kr] 5s² 4d¹⁰ 5p⁶ → outermost n=5: 2+6 = 8
20. Copper (Cu) – Transition metal. Outermost shell is 4s¹ (note: exception configuration). So 1 valence electron? Wait — let’s check.
Actually, copper’s electron configuration is [Ar] 3d¹⁰ 4s¹. So outermost level is n=4, which has only 4s¹ → so 1 valence electron? But wait — many sources say copper has 1 or 2 valence electrons depending on context. However, per the worksheet’s rule: “valence electrons are the electrons in the outermost principal energy level” and “always ‘s’ or ‘s and p’”. Since copper’s outermost level (n=4) has only 4s¹, that’s 1 electron.
BUT — hold on! In many high school contexts, especially with transition metals, they often say “transition metals have 2 valence electrons” because they lose the s electrons first. However, copper is an exception — it’s 4s¹ 3d¹⁰, so technically only 1 in the outermost s orbital.
However, looking back at the worksheet’s example and instructions — it says “they are always ‘s’ or ‘s and p’ electrons”. So for copper, outermost level is n=4, which has only 4s¹ → so 1 valence electron.
But let me double-check common teaching practice: Many textbooks list copper as having 1 or 2 valence electrons. To be safe, let’s see what the pattern is.
Wait — actually, in the periodic table, copper is in Group 11. For main group, Group 11 would be... but it’s transition. The safest way for this worksheet: since the instruction says “outermost principal energy level”, and for Cu it’s 4s¹, then answer is 1.
However, I recall that sometimes copper is considered to have 2 valence electrons because it can form +2 ions. But strictly by definition given: outermost level electrons in s and p orbitals → 4s¹ → 1.
But let me verify with a reliable source mentally: Standard answer for copper in such worksheets is often 1 or 2? Actually, upon second thought — many curricula teach that all transition metals have 2 valence electrons (the ns²), even if exceptions like Cr and Cu exist. But Cu is 4s¹, so it should be 1.
To resolve this: Let’s look at zinc — it’s 4s², so 2. Copper is before zinc, and it’s 4s¹, so 1.
I think for accuracy, we’ll go with 1 for copper.
But wait — let’s check online or standard knowledge: Actually, in many high school chemistry classes, when asked for valence electrons of transition metals without specification, they expect 2. But the worksheet defines it clearly: “electrons in the outermost principal energy level” and “always ‘s’ or ‘s and p’”.
For copper: outermost principal energy level is n=4. Electrons in n=4: only 4s¹ → so 1.
Similarly, chromium is 4s¹ 3d⁵ → 1 valence electron by this definition.
So I’ll go with 1 for copper.
But let me confirm with another approach: The maximum number of valence electrons is 8, and for transition metals, we don’t count d electrons as valence in this context.
Yes, so:
Final answers:
1. fluorine: 7
2. phosphorus: 5
3. calcium: 2
4. nitrogen: 5
5. iron: 2 (outermost 4s²)
6. argon: 8
7. potassium: 1
8. helium: 2
9. magnesium: 2
10. sulfur: 6
11. lithium: 1
12. zinc: 2 (4s²)
13. carbon: 4
14. iodine: 7
15. oxygen: 6
16. barium: 2
17. aluminum: 3
18. hydrogen: 1
19. xenon: 8
20. copper: 1 (4s¹)
Wait — I’m now doubting copper. Let me think again.
In many standardized tests and worksheets, copper is listed as having 1 valence electron because of its configuration. For example, in AP Chemistry, they consider the 4s electron as valence.
Yes, I think 1 is correct.
But to be absolutely sure, let's see: The worksheet says "the valence electrons are the electrons in the outermost principal energy level". For copper, atomic number 29: 1s2 2s2 2p6 3s2 3p6 4s1 3d10. The outermost principal energy level is n=4, which contains only the 4s1 electron. So yes, 1 valence electron.
Okay, final list:
1. 7
2. 5
3. 2
4. 5
5. 2
6. 8
7. 1
8. 2
9. 2
10. 6
11. 1
12. 2
13. 4
14. 7
15. 6
16. 2
17. 3
18. 1
19. 8
20. 1
I think that's accurate based on the definition given.
Final Answer:
1. 7
2. 5
3. 2
4. 5
5. 2
6. 8
7. 1
8. 2
9. 2
10. 6
11. 1
12. 2
13. 4
14. 7
15. 6
16. 2
17. 3
18. 1
19. 8
20. 1
Parent Tip: Review the logic above to help your child master the concept of chemistry if8766 worksheet answers.
