Mass number is the sum of protons and neutrons in the nucleus.

Isotopes are atoms of the same element that have different numbers of neutrons.

Rutherford's gold foil experiment led to the discovery of the dense, positively charged nucleus.

Neutrons are electrically neutral subatomic particles.

The nucleus consists of protons and neutrons, collectively known as nucleons.

The atomic number represents the number of protons in the nucleus of an atom.

The mass of an electron is approximately 1/1836 of the mass of a proton or neutron.

To maintain electrical neutrality, the number of positive protons must equal the number of negative electrons.

Bohr proposed that electrons move in fixed circular orbits around the nucleus.

Valence electrons determine how an atom interacts and bonds with other atoms, thus defining its chemical properties.

The mass number is the sum of protons and neutrons (15+16=31), and phosphorus (P) has an atomic number of 15.

Protons and neutrons have a relative mass of approximately 1 amu, while the electron's mass is negligible (about 1/1836 of a proton).

Isotopes are named by their element name followed by the mass number (protons + neutrons).

A nucleon is any particle that resides in the nucleus, which includes protons and neutrons.

J.J. Thomson used cathode ray tubes to identify the existence of negatively charged particles known as electrons.

The number of neutrons is found by subtracting the atomic number from the mass number: 238 - 92 = 146.

Losing a negatively charged electron leaves the atom with a net positive charge, forming a cation.

The nucleus contains protons and neutrons, which account for over 99.9% of an atom's mass.

Isotopes are atoms of the same element having the same proton count but differing in the neutron count, leading to different mass numbers.