The number of_ in an atom is called its atomic number.

Different isotopes of an element have different mass numbers because they have different numbers of _.

Atoms have equal numbers of _, so they are neutral in electric charge.

Atoms can gain or lose _ and become ions.

The process in which an atom becomes an ion is called _.

The nucleus is a small, dense region

_ (also called electron shells) are fixed distances from the nucleus of an atom where electrons may be found.

Which of the following would NOT be correct? Ionization may occur when:

_ are the basis of the electron cloud model of the atom. This model is still accepted by scientists today.

The idea of the atom was first introduced by the ancient Greek philosopher named _.

Around 1800, the English chemist _ reintroduced the idea of the atom.

In 1897, _ discovered the first subatomic particle, the electron, while researching cathode rays.

_ discovered the nucleus of the atom in 1911. He sent a beam of alpha particles toward gold foil and observed the way the particles were deflected by the gold atoms.

In the _ atomic model, electrons move around the nucleus only at fixed distances from the nucleus based on the amount of energy they have.

In the 1920s, _ proposed that electrons’ exact positions cannot be determined. He developed an equation to calculate where electrons are most likely to be.

Student of Rutherford; he discovered the neutron.

German scientist had the idea of a quantum, a discrete, or distinct, amount of energy.

The nucleus consists of _, so it has an overall _ charge.

_ are the building blocks of matter.

All atoms are very small, but atoms of different _ vary in size.

Electrons in the outermost energy level of an atom are called _. They determine many of the properties of an atom, including how reactive it is.

As you go farther from the nucleus, electrons at higher energy levels have _.

Which of the following are NOT one of the main types of particles that make up all atoms?

Ions are all of the following EXCEPT:

What are positively charged ions called?

What are negatively charged ions called?