atomic structure

What are the relative charges of the three subatomic particles?

• Proton: +1
• Neutron: 0
• Electron: -1

What are the relative masses of the three subatomic particles?

• Proton: 1
• Neutron: 1
• Electron: Very small (often cited as \frac{1}{1840} or \frac{1}{2000})

What does the Atomic Number represent?

The number of protons in the nucleus of an atom, which determines the element.

How is the Mass Number of an atom calculated?

The total number of protons and neutrons in the nucleus: \text{Mass Number} = \text{Protons} + \text{Neutrons}

Define an Isotope.

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

Describe the Plum Pudding Model of the atom.

A model proposed by J.J. Thomson suggesting the atom is a ball of positive charge with negative electrons embedded in it.

What did the Alpha Particle Scattering Experiment prove about the atom?

• Atoms are mostly empty space.
• The mass is concentrated in a central, positively charged nucleus.

What is the maximum number of electrons allowed in the first three energy levels (shells)?

• 1st shell: 2
• 2nd shell: 8
• 3rd shell: 8

What is the approximate size (radius) of an atom?

About 1 \times 10^{-10} metres (or 0.1 nanometres).

How does an atom become a negative ion?

By gaining one or more electrons, resulting in more negative charges than positive protons.