Ex. ---- 5438----- 4 sig figs

.0670----- 3 sig figs

3.0067----- 5 sig figs 

Rules

Any non zero digit is a sig fig

All zeros that follow a decimal point and a nonzero digit are sig fig

All zeros between sig figs are sig figs (sandwich) 

Zero place holders are not sig figs. 

Ex

2.5g(100cg/1g)

Grams cancel out leaving you with centagrams 

D=M/V

Volume is always cubed 

Elements- a substance that cannot be decomposed by any chemical reaction into simpler substances.

Compounds- a substance composed of two or more elements chemically combined.

Mixtures- a material that can be separated by physical means into two or more substances.

heterogeneous- distinct parts 

homogenous- a uniform mixture 

Physical- you can get its parts back, does not change it's chemical identity.

Chemical- cant get its original parts back- one or more kinds of matter are transformed into new matter.

The total mass remains constant during a chemical change.

1- Allall all matter is composed of indivisible atoms.

2- An element is a type of matter composed of only one kind of atom, each atom of a given kind having the same properties.

3- A compound is a type of matter composed of atoms of two or more elements chemically combined in fixed proportions.

4- chemical reaction consist of the rearrangement of the atoms present in the reacting substances to give new chemical combinations present in the substance formed by the reaction. 

Atomic number = protons 

protons + neutrons = atomic number

protons and electrons are equal when a substance is neutral 

protons and neutrons are in nucleus 

protons are positive

neutrons are neutral

electrons are negative

Amu

Amu is atomic mass units

1 amu= 1/12 carbon 12 = 1p,1n

Same atomic number but different atomic mass

Same number of protons nut different number of neutrons.

ex- C12 and C13

Roygbiv going from low freq. high wave length to high freq. low wave length. 

Frequancy= energy 

high freq. = high energy

low freq. = low energy 

wave length and frequancy is given out when an electron moves from level to level, emits light= must go down 

Deduced by Dalton from ibis atomic theory states that, when two elements form more than one compound, the masses of one elements in these compounds for a fixed mass of the other element are in ratios of small whole numbers. 

Ratio is always the same 

Nuclear model

Most of the mass of the Atom is concentrated in a positively charged center or nucleus around which the negatively charged electrons move. 

began research on the discharge of electricity through gases, in 1897 he discovered the electron. 

Cathode

C= f x wavelength 

be careful of units 

1m= 1x10^9nm