Chem H the atom

Dalton’s Atomic Theory

• all matter is composed of tiny particles called atoms

• atoms of the same element are identical; atoms of different elements are different

• atoms cannot be subdivided, created, or destroyed

• atoms of different elements combine in small whole number ratios to form compounds

• in chemical reactions, atoms are combined, separated, or rearranged

incorrect pieces of Dalton’s atomic theory

• atoms of the same element are identical; atoms of different elements are different ——→ isotopes exist with different masses

• atoms cannot be subdivided, created, or destroyed ————> subatomic particles (subdivided) & nuclear reactions can change elements

Bohr

planetary model of the atom

Dalton

billiard ball model, but no subatomic particles

Thomson

• plum pudding model

• discovered electrons —————→ using cathode ray

Rutherford

discovered the positive nucleus —————> gold foil experiment

Chadwick

discovered neutrons

subatomic particles

proton, neutron, electron

proton

• found in nucleus

• positive (+)

• 1 amu

neutron

• found in nucleus

• no charge (neutral)

• 1 amu

Electron

• found in energy levels

• negative (-)

atomic number

the number of protons in the nucleus of the atom

mass number

the number of protons + neutrons in the nucleus

number of protons

atomic number

number of electrons

atomic number (for a neutral atom)

number of neutrons

mass number - atomic number

isotopes

atoms of the same element that vary in their number of neutrons (same atomic number but different mass number)

average atomic mass

the weighted average of the masses of the known naturally occurring isotopes of the element; unit is amu

average atomic mass formula

avg. atomic mass = (mass)(%) + (mass)(%) / 100

nuclear notation

hyphen notation

carbon - 14 (dash is the mass number)

ion

an atom that has lost or gained one or more electron(s)

cation

positively charged ion [atom has lost electron(s)]

anion

negatively charged ion [atom has gained electron(s)]

alpha emission

• an alpha particle is made of two protons and two neutrons bound together and emitted from the nucleus during some kind of radioactive decay

• used in smoke detectors

• +2 charge, slowest and least penetrative

beta emission

• a beta particle is an electron emitted from the nucleus during some kind of radioactive decay

• negative charge

gamma emission (ray)

• high-energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground energy state

• used to detect and treat cancer

• highest energy, used to treat cancer cells