Unit 9- Periodic Table

Aristotle

said that all matter was continuous

Democritus

Proposed the idea of the atom

Dalton's Atomic Theory

All elements are made of atoms
1) All elements are made of atoms
2)All atoms of the same element are identical (wrong)
3)Atoms of different elements combine with other atoms in whole number ratios
4)Reactions occur when atoms are separated, joined, or rearranged (later on nuclear chemistry was also discovered

Thompson

1) Discovered the electron (using a cathode ray tube)
2) Discovered that electrons are negatively charged and they have mass
3) Made the "Plum Pudding Model"

Rutherford

Who performed the Gold foil experiment?

Gold foil experiment

1) Discovered the proton and the nucleus
Conclusions
1) Atoms have a small positive center that contains positively charged protons
2) The nucleus makes up almost all of the atom's mass
3) Atoms are mostly empty space

Chadwick

Discovered the neutral neutron in the nucleus (has no charge, but has mass)

Bohr

He made the planetary model of the atom

Electron cloud model

A modern model of an atom

Electron Cloud Model

Using probability models, scientists can predict a cloud of where electrons are 90% of the time.

Proton

Positive charge (+1)
Mass= 1 amu

Neutron

0 charge
Mass= 1 amu

Electron

Negative charge (-1)
Mass= 1/1837 amu

Atomic Mass Unit

amu stands for

Dalton

Who used circular symbols to represent the elements?

Berzelius

Suggested the use of letters to symbolize elements

Mendeleev

Organized the first periodic table

Atomic #

The number of protons (which is equal to the number of electrons)

Mass number

The sum of the number of protons and neutrons (round the atomic mass, which is only an average)

How to calculate Neutrons

M.A.N
M-A=N
M= Mass
A= Atomic #
N= Neutrons

Isotopes

An atom with the same number of protons, but a different # of neutrons (the exception to "all atoms of an element are identical")

Mendeleev

Noticed there was a pattern in chemical properties every 8 elements with increasing atomic mass

Moseley

Perfected the arrangement of the elements by placing them in order of atomic number instead of atomic mass.

Groups/ Families: Vertical Columns

Have similar chemical properties
Have the same # of electrons in their outer shell

Periods

Horizontal rows of elements in the periodic table

Metals

All elements to the left of the zig- zag line on the PT
Have some common properties
1) Solids at room temp. except for mercury
2) Shiny (Luster)
3) Good conductors (heat and electricity)
4) Ductile- can be rolled into wire
5) Malleable- can be pounded into sheets

Non- Metals

All elements to the right of the zig- zag line on the periodic table.
Have common properties (gases at room temp., do not conduct heat or electricity)

Metalloids

Next to the zig- zag line
Have properties of both metals and non- metals

Alkali Metals

Group 1
Li, Na, K, Rb, Cs, Fr
Shiny, highly reactive in water
Lose an electron to form a +1 charge

Alkaline Earth Metals

Group 2
Be, Mg, Ca, Sr, Ba, Ra
Shiny, highly reactive in water
Lose 2 electrons to form a +2 charge

Transition Metals

Groups 3-12 on the Periodic Table
Less active than metals in groups 1 and 2

Nonmetals and other elements

Dull (not shiny)
Brittle and powdery (not malleable nor ductile)
Poor conductors

Hydrogen

Makes up 90% of all the atoms in the universe
Diatomic molecule (has 2 atoms of the same element)- H2
Highly reactive because it has 1 electron

Halogens

Group 17/7
Means "salt former"
Have 7 electrons and want to gain one more to form a -1 charge
*group 1 and 17 will often combine to form a neutral molecule

The Noble Gases

Group 18/8
Very stable and unreactive
Have a full outer energy level (8 electrons)

The Boron Group

Group 13/3

The Carbon Group

Group 14/4

The Nitrogen Group

Group 15/5

The Oxygen Group

Group 16/6