3.1 the atom and its parts Chem 101

Atom

The smallest piece of an element that maintains the identity of that element

The concept that atoms play a fundamental role in chemistry is formalized by

Modern Atomic Theory

What is the first part of modern atomic theory

All matter is composed of atoms

What is the second part of modern atomic theory

Atoms of the same element are the same; atoms of different elements are different.

What is the third part of modern atomic theory

Atoms combine in whole-number ratios to form compounds.

Electron e^-

a tiny subatomic particle with a negative charge that orbits the center of the atom

Proton p⁺

a relatively massive (but still tiny) subatomic particle with a positive charge

Neutron n⁰

a subatomic particle with about the same mass as a proton but no charge.

Who first pointed out a nuclear model?

Ernest Rutherford in England in the 1910s

What is the center of an atom called where the protons and neutrons are collected?

Nucleus

Where are the electrons located?

Orbiting outside the nucleus

Atomic number

The number of protons the atom has in its nucleus which determines the element

Isotopes

Atoms of the same element can have different numbers of neutrons while maintaining the same number of protons.

Mass number

The sum (+) o

f the number of protons and neutrons in the nucleus

Neutral atoms have what number of electrons compared to protons?

the same, the overall charge is zero