Chem Unit 2

Democritus

came up with term atom and hypothesized it makes up all matter and can’t split (hence the name)

Alchemists

experimented with chemicals/elements to make gold, silver, or immortality, but ended up discovering many more elements

Robert Boyle

defined element as a sampled of matter that can’t be broken down into simpler substances and recognized importance of careful measurement

John Dalton’s Atomic Theory

1. Element are made of atoms ~ True

2. All atoms of an element are identical ~ True

3. Atoms of an element are specific to that element ~ True

4. Atoms of different elements combine to make compounds ~ True

5. Atoms can’t be created or destroyed ~ False

J. J. Thomson

Used the cathode ray tube and magnets to discover the electron

William Thomson/Lord Kelvin

created atomic(plum pudding) model where negative particals are balanced by positive material surrounding it like raisins in a pudding

Hantara Nagoka

developed Saturnian system in which electrons orbit a nucleus in rings

Ernest Rutherford

used gold foil experiment to determine atoms contained a positive center with mostly open space

Neils Bohr

used previous discoveries to describe atom with positive nucleus and negative electrons orbiting in rings outside nucleus ~ Bohr’s model

Energy Levels

atoms have a series of principal energy levels which correspond to each row and symbolized by n

sublevel

made up of different types of orbitals

1. S ~ 1 orbital

2. P ~ 3 orbitals

3. D ~ 5 orbitals

4. F ~ 7 orbitals

Orbital/Electron Cloud

probability map of an electron and contains up to two electrons per orbital

Valence Electrons

electrons in the last energy level

Pierre Joseph Pelletier

discovered chlorophyll, caffeine, strychnine, colchicine, and quinine

William Perkin

produced synthetic dye called mauve

Dmitri Mendeleev

elements listed in vertical columns in order of increasing atomic mass; left space for new discoveries which perfectly fit; similar elements were side by side

Henry Mosely

found charge of elements’ atom and arranged elements in table by order of atomic number

Periodic Law

arrangement of increasing atomic # correlates with physical and chemical properties

Periods

rows of table

Groups

columns of table

Periodic Trends

due to attraction of valence electrons and nucleus

As table moves to right

more protons so nucleus gets more positive which increases reaction

as table moves down

shields increase which reduces attraction and separates valence from nucleus

Atomic Radius

distance from nucleus to valence

moving right decreases; moving down increases

Ionization Energy

energy required to remove electron from atom

moving right increases; moving down decreases

Electronegativity

how strongly nucleus attracts electrons of dif atom in a bond

moving right increases; moving down decreases