C1 - Atomic Structure and the Periodic Table

What three subatomic particles make up an atom?

Protons, neutrons, and electrons.

State the charge and relative mass of a proton.

Charge = +1, Relative mass = 1

State the charge and relative mass of a neutron.

Charge = 0, Relative mass = 1

State the charge and relative mass of an electron

Charge = -1

Relative mass = ≈0

Where are the subatomic particles found in the atom?

Protons and neutrons in the nucleus; electrons in shells.

What does the atomic number represent?

The number of protons

What does the mass number represent?

The total number of protons + neutrons

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons.

How do you calculate the number of neutrons?

Neutrons = Mass number − Atomic number.

What is an ion?

An atom that has gained or lost electrons.

Who discovered the nucleus?

Rutherford (gold foil experiment).

Who discovered the electron?

J.J. Thomson.

What did the gold foil experiment show?

Atoms have a small, dense, positive nucleus and are mostly empty space.

Q: What did Bohr propose about electrons?

They orbit the nucleus in fixed energy levels (shells).

How are elements arranged in the periodic table?

By increasing atomic number.

What do elements in the same group have in common?

The same number of electrons in their outer shell.

What are the noble gases?

Group 0 — very unreactive because they have a full outer shell.

What are the alkali metals?

Group 1 — soft, reactive metals (e.g. lithium, sodium, potassium).

What happens to reactivity down Group 1?

Increases (electrons are lost more easily).

What are the halogens?

Group 7 — non-metals that form salts.

What happens to reactivity down Group 7?

Decreases (harder to gain an electron)