Chapter 4 Chemistry Review

oxygen

-most abundant in element in the atmosphere
-most abundant element in body

trace amonts

really tiny amounts of an element

elements

building blocks for all matter
-single atom of element
-molecules of an element found in natural state

O

oxygen

F

fluorine

I

iodine

Kr

Krypton

Li

lithium

C

carbon

diatomic elements

2 atoms make up one molecule
-oxygen
-hydrogen
-nitrogen

Dalton's Diatomic Thoeory

proposed modern atomic model based on experimentation and not reason; his ideas account for Law of Conservation of Mass and Law of Constant Composition (elements combine in fixed ratios)

compound

substance produced when 2 or more elements combine in a chemical reaction (ex: hydrogen and oxygen combine to make water)

2H(2)O

2 x 2 plus 2 x 1 equals 8 molecules

JJ Thomson

in 1897, he said that atoms contain electrons; used cathode ray to deduce the presence of negatively charge particle, an electron

cathode

plus

anode

-

William Thomson (Lord Kelvin)

plum pudding model; electrons with - charge scattered around to balance positive charge

Ernest Rutherford

directed alpha particles inside circular foil; proved the plum pudding model as INCORRECT; concluded that the atom has a tiny, positively charged center called the nucleus

atom

tiny dense center with positive charge called the nucleus; electrons travel around the nucleus; a proton has the same magnitude of charge as the electron, but its charge is positive

proton

positive charge; in nucleus;
atomic number
mass: 1

neutron

no charge; in nucleus; 0

electron

negative charge; move around the nucleus; mass: 1

Rutherford and Chadwick

most nuclei contain neutral particle called neutron; neutron slightly more massive than proton, but has no charge

nucleus

small overall but extremely dense; accounts for all of the atom's mass; contains protons and neutrons

electron cloud

makes up most of the volume of an atom;
mostly empty space
; negatively charged

Why do diff atoms have diff chemical properties?

-the chemistry of an atom arises from its electrons
-electrons are the parts of atoms that "intermingle" when atoms combine to form molecules
-it is the number of electrons that determines chem behavior

valence electrons

outer shell of electrons

isotopes

atoms with same number of protons but different numbers of neutrons

atomic number

number of protons (and also electrons)

atomic mass

number of protons and neutrons in atoms

how to find number of neutrons

atomic mass - atomic number

Dmitri Mendeleev

-ordered elements by increasing atomic mass

periodic law

when elements are arranged in order of increasing relative mass, certain sets of properties recur periodically

properties of metals

-good conductor
-malleable
-ductile
-high density

combined form elements

-noble gases: gold, platinum, silver
-noble gases: group 8

alletropes

different forms of a different element

solid carbon

4th allotrope- graphine

ions

atoms can form ___ by gaining or losing electrons

group 1 and 2

form 1 plus and 2 plus ions

group 3

form 3 plus ions

group 7

form anions with -1 charges

group 6

form anions with -2 charges

ionic compounds

electrically neutral; charges on the anions must sum to zero; must have net charge of zero

isotopes

atoms of same element that differ in mass number (differing number of neutrons)