Students fill in atomic details like protons and neutrons on this periodic table practice sheet.

Let’s solve this step by step.

We are given a worksheet with 9 boxes (3 rows × 3 columns). Each box is for one element, and we need to fill in missing info using the periodic table and basic atomic structure rules:

Rules to remember:
- Atomic Number = number of protons = number of electrons (in a neutral atom)
- Atomic Mass ≈ protons + neutrons → so neutrons = atomic mass - atomic number
- Round atomic mass to nearest whole number if needed
- Symbol is the standard chemical symbol (e.g., H for Hydrogen, Hg for Mercury)

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Box 1: Hydrogen (given)
- Name: Hydrogen
- # of protons: 1 → so atomic number = 1
- # of neutrons: 0 → so atomic mass = 1 + 0 = 1
- Symbol: H
- # of electrons: same as protons → 1

✔ Already filled correctly.

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Box 2: Symbol = Hg

Hg is Mercury.

From periodic table:
- Atomic number of Hg = 80 → so protons = 80, electrons = 80
- Atomic mass of Hg ≈ 200.59 → round to 201
- Neutrons = 201 - 80 = 121

So:
Name: Mercury
Atomic Number: 80
Atomic Mass: 201
Symbol: Hg
# of protons: 80
# of electrons: 80
# of neutrons: 121

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Box 3: # of electrons = 19

In neutral atom, electrons = protons = atomic number → atomic number = 19

Element with atomic number 19 is Potassium → symbol K

Atomic mass of K ≈ 39.10 → round to 39

Neutrons = 39 - 19 = 20

So:
Name: Potassium
Atomic Number: 19
Atomic Mass: 39
Symbol: K
# of protons: 19
# of electrons: 19
# of neutrons: 20

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Box 4: Atomic Mass = 35, # of neutrons = 18

Neutrons = atomic mass - atomic number → 18 = 35 - atomic number → atomic number = 35 - 18 = 17

Element with atomic number 17 is Chlorine → symbol Cl

Protons = 17, electrons = 17

So:
Name: Chlorine
Atomic Number: 17
Atomic Mass: 35
Symbol: Cl
# of protons: 17
# of electrons: 17
# of neutrons: 18

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Box 5: # of protons = 2

Atomic number = 2 → Helium → symbol He

Atomic mass of He ≈ 4.00 → round to 4

Neutrons = 4 - 2 = 2

Electrons = 2

So:
Name: Helium
Atomic Number: 2
Atomic Mass: 4
Symbol: He
# of protons: 2
# of electrons: 2
# of neutrons: 2

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Box 6: # of electrons = 4

→ atomic number = 4 → Beryllium → symbol Be

Atomic mass of Be ≈ 9.01 → round to 9

Neutrons = 9 - 4 = 5

Protons = 4

So:
Name: Beryllium
Atomic Number: 4
Atomic Mass: 9
Symbol: Be
# of protons: 4
# of electrons: 4
# of neutrons: 5

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Box 7: Symbol = S

S is Sulfur.

Atomic number of S = 16 → protons = 16, electrons = 16

Atomic mass of S ≈ 32.07 → round to 32

Neutrons = 32 - 16 = 16

So:
Name: Sulfur
Atomic Number: 16
Atomic Mass: 32
Symbol: S
# of protons: 16
# of electrons: 16
# of neutrons: 16

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Box 8: # of protons = 9

Atomic number = 9 → Fluorine → symbol F

Atomic mass of F ≈ 19.00 → round to 19

Neutrons = 19 - 9 = 10

Electrons = 9

So:
Name: Fluorine
Atomic Number: 9
Atomic Mass: 19
Symbol: F
# of protons: 9
# of electrons: 9
# of neutrons: 10

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Box 9: Atomic Number = 29

Element with atomic number 29 is Copper → symbol Cu

Atomic mass of Cu ≈ 63.55 → round to 64

Neutrons = 64 - 29 = 35

Protons = 29, electrons = 29

So:
Name: Copper
Atomic Number: 29
Atomic Mass: 64
Symbol: Cu
# of protons: 29
# of electrons: 29
# of neutrons: 35

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Now let’s compile all answers into the grid format as requested.

Final Answer:

Row 1:
- Box 1: Name: Hydrogen, Atomic Number: 1, Atomic Mass: 1, Symbol: H, # protons: 1, # electrons: 1, # neutrons: 0
- Box 2: Name: Mercury, Atomic Number: 80, Atomic Mass: 201, Symbol: Hg, # protons: 80, # electrons: 80, # neutrons: 121
- Box 3: Name: Potassium, Atomic Number: 19, Atomic Mass: 39, Symbol: K, # protons: 19, # electrons: 19, # neutrons: 20

Row 2:
- Box 4: Name: Chlorine, Atomic Number: 17, Atomic Mass: 35, Symbol: Cl, # protons: 17, # electrons: 17, # neutrons: 18
- Box 5: Name: Helium, Atomic Number: 2, Atomic Mass: 4, Symbol: He, # protons: 2, # electrons: 2, # neutrons: 2
- Box 6: Name: Beryllium, Atomic Number: 4, Atomic Mass: 9, Symbol: Be, # protons: 4, # electrons: 4, # neutrons: 5

Row 3:
- Box 7: Name: Sulfur, Atomic Number: 16, Atomic Mass: 32, Symbol: S, # protons: 16, # electrons: 16, # neutrons: 16
- Box 8: Name: Fluorine, Atomic Number: 9, Atomic Mass: 19, Symbol: F, # protons: 9, # electrons: 9, # neutrons: 10
- Box 9: Name: Copper, Atomic Number: 29, Atomic Mass: 64, Symbol: Cu, # protons: 29, # electrons: 29, # neutrons: 35