Download Study Guide Chapter 11 – Introduction to Atoms

Study Guide Chapter 11
Atom – the smallest particle into which an element can be divided and still be the same substance.
Dalton – developed the first modern atomic theory
Thomson – discovered there are small particles inside the atom called electrons
A. Plum pudding model – electrons mixed throughout the atom
Rutherford – discovered that atoms are mostly empty space with a dense, positive nucleus
A. Rutherford model – dense nucleus with electrons surrounding at a distance
Nucleus – an atom’s central region, which is made up of protons and neutrons
Bohr’s model – electrons move around the nucleus in certain paths called energy levels
Electron cloud model – (model theory) a region around the nucleus of an atom where electrons are likely
to be found
Protons – positively charged particles in the nucleus
Neutrons – particles of the nucleus that have no charge
Electrons – negatively charge particles found around the nucleus in electron clouds
Ion – if the charges are not equal between protons and electrons, you have a charged particle
Atomic number – the number of protons in the nucleus of an atom
Isotope – atoms that have the same number of protons but have different number numbers of neutrons
Radioactive – an isotope that is an atom with a nucleus that will change over time
Mass number – the sum of the numbers of protons and neutrons in the nucleus of an atom
Atomic mass – the weighted average of the masses of natural isotopes of an element
Forces in the atom
A. Gravitational Force – pulls objects towards each other
B. Electromagnetic force – opposite charges attract and same charges repel
1. force that holds electrons around the nucleus
C. Strong Force – keeps a nucleus with 2 or more protons from flying apart
D. Weak Force – allows a neutron to change into a proton or electrons in certain unstable atoms