Isotopes & Atomic Structures

What is an isotope?

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

What is the atomic number?

The number of protons in an atom.

What is the mass number?

The sum of protons and neutrons in an atom.

What is average atomic mass?

Weighted average of all naturally occurring isotopes of an element.

Standard isotope notation shows which three pieces of information?

Mass number, atomic number, element symbol.

How are opposite charges in atoms related?

Opposite charges attract; electrons are drawn to the positively charged nucleus.

How do like charges in atoms interact?

Like charges repel; electrons push each other to higher energy levels if crowded.

In what order do electrons fill energy levels?

Level 1 \rightarrow Level 2 \rightarrow Level 3 (closest to farthest from nucleus).

Maximum electrons in Level 1?

2 electrons.

Maximum electrons in Level 2?

8 electrons.

Maximum electrons in Level 3?

18 electrons.

Formula for charge of an atom?

Charge = #protons - #electrons.

Formula for number of electrons?

Electrons = #protons - charge.

Formula for number of neutrons?

Neutrons = Mass number - Atomic number.

Formula for mass number?

Mass = #protons + #neutrons.

Formula for atomic number?

Atomic number = #protons.

Formula for average atomic mass?

Average Atomic Mass (isotope mass \times relative abundance)/100

Relative abundance in average atomic mass calculations is expressed as?

It’ll often be a decimal number as it includes all isotopes. Example: 40.22

What defines an element?

The number of protons in an atom.

Charge of a proton?

+1 .

Charge of a neutron?

0 (neutral).

Charge of an electron?

-1

Relative mass of a proton?

1 amu.

Relative mass of a neutron?

\sim 1 amu.

Relative mass of an electron?

\sim 0 amu. (It’s almost nothing compared to electrons and neutrons (not counted in mass)

Location of protons and neutrons?

Nucleus.

Location of electrons?

Energy shells (surrounds nucleus)