chem unit 4

unit 4 chemistry honors vocabulary + key ideas

nuclear model

nuclear model

contains positively charged nucleus (no distinct protons) and electrons. most of the atom is empty space. RUTHERFORD

solid sphere model

cannot be divided up into smaller parts. DALTON

proton model

nucleus consists of protons and electrons, which circle the nucleus — similar to nuclear model. CHADWICK and RUTHERFORD

plum pudding model

positive fluid, no nucleus, electrons scattered throughout. THOMSON

solar system model

nucleus at center (no distinct protons), electrons circle it at specified orbits. different distances from nucleus. BOHR

who discovered electrons?

thomson

who discovered protons?

rutherford

who discovered the nucleus?

rutherford, did NOT know about neutrons

who discovered neutrons?

rutherford / chadwick

how were electrons discovered?

cathode ray experiment (thomson)

how was the nucleus discovered?

gold foil experiment (rutherford)

how were neutrons discovered?

beryllium / boron / lithium sheet experiment (chadwick)

how were protons discovered?

scintillation detectors (in progress)

law of the conservation of mass

matter is neither created nor destroyed, just converted in some way

dalton’s atomic theory

- matter is made up of small particles called atoms

- atoms are indivisible and indestructible

- atoms of a particular element are identical in size, mass, and chemical properties

- atoms of other elements differ from each other

- different atoms combine in simple whole-number ratios to form compounds

- chemical reaction: atoms are separated, combined, and rearranged

isotope

same element: same number of protons but different number of neutrons in the nucleus

mass number

total number of neutrons and protons

atomic number

number of protons

atomic mass

similar to mass number, but includes the electrons, so it is an approximation of an atom’s total mass

radioactive decay

emission of energy in the form of ionizing radiation

fusion

joining of 2 nuclei to form a larger nucleus. accompanied by a large amount of energy (e.g. hydrogen bombs)

fission

separation of a nucleus into 2 smaller nuclei. accompanied by a large amount of energy

electron, proton, neutron, gamma, beta, alpha symbols

e-, p+, n^o, γ, β, α (gamma and alpha are different)

beta decay (particles)

electron is emitted from a radioactive nucleus (neutron becomes proton, gives off electron; when writing an equation with β-, atomic # gains a proton. with β+, atomic # loses a proton.) negative charge, no mass

alpha decay (particles)

2 protons and 2 neutrons produced during alpha decay. 2 protons, 4 atomic mass

gamma radiation / particles

emitted from a radioactive nucleus. no charge, no mass

nuclear chain reaction

a series of reactions following fission, where the emitted neutrons can cause additional fission reactions.

average atomic mass of an isotope

1. change percent of abundance into decimal (divide by 100)

2. multiply by atomic mass

3. add together to get the average.

use % of abundance and mass number/actual mass