Free Printable Atomic Structure Worksheets - Free Printable

Here is the completed Basic Atomic Structure Worksheet with clear explanations for each answer:

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① The central part of the atom is called the _nucleus_

✔ Explanation: The nucleus is the dense core at the center of an atom, containing protons and neutrons.

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② Electrons are found _outside_ the nucleus.

✔ Explanation: Electrons orbit the nucleus in regions called electron shells or orbitals. They are not inside the nucleus.

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③ The nucleus has a _positive_ charge and contains _protons_ and _neutrons_.

✔ Explanation: Protons are positively charged; neutrons have no charge. Together, they make up the nucleus, which therefore has a net positive charge.

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④ The _proton_ and the _neutron_ have the same mass.

✔ Explanation: Both protons and neutrons have a mass of approximately 1 atomic mass unit (amu). Electrons are much lighter (~1/1836 amu).

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⑤ Give the charge of each:

- Proton _+1_
- Neutron _0_
- Electron _–1_

✔ Explanation:
- Proton = +1 elementary charge
- Neutron = neutral (0 charge)
- Electron = –1 elementary charge (equal in magnitude but opposite to proton)

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⑥ Order from the lightest to heaviest: _Electrons, Protons, Neutrons, Nucleus_

✔ Explanation:
- Electron ≈ 0.0005 amu
- Proton ≈ 1 amu
- Neutron ≈ 1 amu (slightly heavier than proton, but often considered equal)
- Nucleus = total mass of protons + neutrons → heaviest

So: Electrons < Protons ≈ Neutrons < Nucleus

*(Note: Since protons and neutrons are nearly equal, either order between them is acceptable, but nucleus is always heaviest.)*

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⑦ The _atomic mass_ of an element is the average mass of an element’s naturally occurring atoms, or isotopes, taking into account the _abundance_ of each isotope.

✔ Explanation: Atomic mass (or atomic weight) is a weighted average based on how common each isotope is in nature.

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⑧ The _mass number_ of an element is the total number of protons and neutrons in the _nucleus_ of the atom.

✔ Explanation: Mass number = protons + neutrons. It applies to a specific isotope, not the whole element.

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⑨ The mass number is used to calculate the number of _neutrons_ in one atom of an element. In order to calculate the number of neutrons you must subtract the _atomic number_ from the _mass number_.

✔ Explanation:
Number of neutrons = Mass number – Atomic number
Atomic number = number of protons

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⑩ Answer the following questions about the ²⁰Ne₁₀ atom:

> Note: The notation “²⁰Ne₁₀” is unusual — normally it’s written as ²⁰Ne, where the 20 is the mass number and the atomic number (10) is implied by the element symbol Ne (Neon). But since it’s written as ²⁰Ne₁₀, we’ll use both numbers.

#### a) No. of protons = 10

✔ Atomic number = number of protons = 10

#### b) No. of neutrons = 10

✔ Mass number – atomic number = 20 – 10 = 10

#### c) No. of electrons = 10

✔ In a neutral atom, # electrons = # protons = 10

#### d) Mass number = 20

✔ Given in the symbol: superscript 20

#### e) Atomic number = 10

✔ Given in the symbol: subscript 10 (also confirmed by element Ne = Neon, atomic number 10)

#### f) No. of valence electrons = 8

✔ Neon (Ne) is a noble gas in Group 18. Its electron configuration is 1s² 2s² 2p⁶ → outer shell (n=2) has 8 electrons → full octet → 8 valence electrons.

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## ✔ Final Completed Worksheet Answers:

① nucleus
② outside
③ positive, protons, neutrons
④ proton, neutron
⑤ Proton: +1, Neutron: 0, Electron: –1
⑥ Electrons, Protons, Neutrons, Nucleus *(or Electrons, Neutrons, Protons, Nucleus — since protons/neutrons ≈ same mass)*
⑦ atomic mass, abundance
⑧ mass number, nucleus
⑨ neutrons, atomic number, mass number
⑩
 a) 10
 b) 10
 c) 10
 d) 20
 e) 10
 f) 8

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