Atomic Theory Flashcards

by Olivia Rahman

Atom

The smallest unit of matter.

Democritus

Greek philosopher who proposed that matter is made of indivisible particles.

Law of Conservation of Matter

Matter cannot be created or destroyed, only rearranged.

Dalton’s Atomic Theory

Stated that all matter is made up of indestructible, unique atoms that combine to form compounds.

J.J. Thompson

Discovered electrons using a Crookes tube.

Bohr Model

Model showing electrons orbiting the nucleus in specific energy levels.

Element

A pure substance made of only one type of atom.

Compound

Two or more different elements chemically combined in fixed amounts.

Proton

Positively charged subatomic particle found in the nucleus.

Neutron

Neutral subatomic particle with no charge found in the nucleus.

Electron

Negatively charged subatomic particle orbiting outside the nucleus.

Atomic Number

The total number of protons in an atom’s nucleus.

Mass Number

The total number of protons and neutrons in an atom's nucleus.

Calculation for number of neutrons

Subtract the atomic number from the mass number.

An atom has 13 protons and 10 electrons. What is its symbol?

Al3+

An atom has 9 protons and 10 electrons. What is its symbol?

F-1

How many neutrons are in an atom with mass number 14 and 7 protons?

7 neutrons

Maximum electrons that can fit in energy level 2

8 electrons

What determines the identity of an element?

The number of protons.

Maximum electrons that can fit in energy level 1

2 electrons