Chemistry notes unit 3

All atoms of an element have the same number of __________.

Protons

An atom is considered __________, having a net charge of zero.

Neutral

The number of protons is equal to the number of __________ in a neutral atom.

Electrons

Atomic mass is the __________ of all the atomic masses of the isotopes of that atom.

Weighted average mass

Mass number counts the number of __________ and __________ in an atom.

Protons and neutrons

Atoms of the same element with different mass numbers are called __________.

Isotopes

Atoms with a __________ (positive or negative) charge are known as ions.

Charge

If __________ change, a new element is formed.

Protons

If electrons change, a new __________ is formed.

Ion

Joseph Priestley(1774) discovered __________ and other gases.

Oxygen

Antonine Lavoisier (1778) is known as the father of __________ chemistry.

Modern

Alessandro Volta (1799)invented the __________, the first chemical battery.

Voltaic pile

John Dalton (1803)developed atomic __________ and the concept of atomic weight.

Theory

Humphrey Davy's (1807)discoveries included several alkali and __________ earth metals.

Alkaline

Dimitri Mendeleev (1869)created the __________ table of elements.

Periodic

JJ Thomson (1897)discovered the __________ and proposed the plum pudding model.

Electron

Marie Curie (1898)conducted pioneering research on __________.

Radioactivity

Robert A. Millikan (1909)measured the charge of the __________ through his oil drop experiment.

Electron

Ernst Rutherford(1910) discovered the __________ through his gold foil experiment.

Nucleus

Harry Moseley's(1913) work led to the redefinition of __________ numbers.

Atomic

James Chadwick (1932)discovered the __________, providing insight into atomic structure.

Neutron

The plum pudding model was proposed by __________ in 1904.

J.J. Thomson

The number of protons in hydrogen is __________.

1

The atomic number of carbon is __________.

6

The average atomic mass accounts for the __________ forms of atoms of an element.

Different

Atoms of the same element have the same number of __________ but can have different numbers of neutrons.

Protons