Chemistry Unit 2 pg. 1-4 notes

What does the atomic number represent in an atom?

represents the number of protons in the nucleus.

How is the mass number of an atom calculated?

by adding the number of protons and neutrons in the nucleus.

What is the charge and relative mass of a proton?

has a positive charge (+) and a relative mass of 1.

What is the charge and relative mass of a neutron?

has no charge (neutral) and a relative mass of 1.

What is the charge and relative mass of an electron?

has a negative charge (-) and a relative mass of approximately 0.

What are isotopes?

atoms that have the same number of protons but different numbers of neutrons.

Who proposed the atomic theory that all elements are made of indivisible particles called atoms?

John Dalton

What did Rutherford discover in 1911?

the nucleus of the atom.

What model of the atom did Bohr propose in 1913?

the planetary model of the atom.

What did Thomson discover in 1897?

the electron.

What is the significance of the number of protons in an atom?

proton # defines the element.

What happens to the number of protons and electrons in a neutral atom?

the number of protons equals the number of electrons.

What is the role of neutrons in the nucleus?

helps keep protons from repelling each other due to their positive charges.

What is the formula for calculating mass number?

Mass Number = Protons + Neutrons.

What does Dalton's Atomic Theory state about atoms of the same element?

states that all atoms of the same element are identical.

What occurs during a chemical reaction according to Dalton's Atomic Theory?

During a chemical reaction, atoms are joined together, separated, or rearranged.

What is the significance of the mass of an electron in atomic mass calculations?

is negligible and does not significantly affect the total mass of an atom.

What is the relationship between protons and atomic number?

The atomic number is always equal to the number of protons in an atom.