the atom

Dalton's Atomic Theory

the first theory to relate chemical changes to events at the atomic level

John Dalton ideas

-atoms of an element are identical, different elements have different atoms

-atoms can't be divided and make up all substances

-atoms join to make new substances

Thompson theory

Plum pudding model

Thompson Theory 1897

-plum pudding model- atom is a positively charged sphere with electrons dotted inside -used a cathode-ray tube to conduct an experiment which showed that there are small particles inside atoms

-disproved Dalton that atoms couldn't be split

Rutherford theory

gold foil method which identified a dense nucleus due to some alpha particles deflecting, bouncing back or going straight through foil.

Rutherford ideas

-proposed atoms were made up of a positive nucleus with negative electrons orbiting around

-later discovered the proton

Chadwick theory

the existence of the neutron

improved understanding of atomic structure, highlighting that atoms are composed of protons, electrons, and neutrons, thereby explaining the mass of atoms and the stability of the atomic nucleus, which could not be accounted for by protons alone.

charge of proton

positive

mass of proton

1

charge of electron

negative

mass of electron

0

charge of neutron

no charge

mass of neutron

1/1836

the nucleus

-protons and neutrons

-positive charge

number of protons

number of electrons

atomic number

the number of protons in the nucleus of an atom

mass number

the total number of protons and neutrons in a nucleus.

isotope

An atom with the same number of protons and a different number of neutrons from other atoms of the same element.

ion

An atom or group of atoms that has a positive or negative charge.