Chemistry Test Chapter 4

Proton

positive(+1)

Electron

negative(-1)

Neutron

neutral(0)

Charge of ions

#of protons-#of electrons-

Mass number of elements equation

protons+neutrons

Mendaleev

gets credit for the periodic table

Dalton's atomic theory

matter is composed of atoms

that atoms of a given element have unique properties that distinguish them from atoms of other elements

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

J. J. Thomson

discovered the electron

Used a plum pudding model

proposed that the negativly charged electrons were small particles held within a positivley charged sphere

Ernest Rutherford

proposed the nuclear theory of the atom based on experiments in which he bombarded ultrathin sheets of gold foil with alpha particles.

Nuclear Theory

most of an atom's mass and all of its positive charge are contained in a small core called the nucleus

Most of the volume of the atom is empty space occupied by tiny, negatively charged electrons

There are as many negatively charged electrons outside the nucleus as there are positively charged particles (protons) inside the nucleus.

The atom is electrically neutral

The nucleus of the atom

contains positively charged protons and neutral particles called neutrons

Similar masses

Protons and Neutrons (about 1 amu)

The periodic law

when elements are arranged in order of increasing atomic number, certain sets of properties recur periodically

Metals

good conductors of heat and electricity, malleable, ductile, often shiny, and tend to lose electrons when they undergo chemical change

tend to loose valence electrons to form positive ions

Nonmetals

poor conductors of heat and electricity and tend to gain electrons when they undergo chemical change

tend to gain valence electrons to form negative ions

Metalloids

semiconductors of electricity

Cations

positivly charged ions

Anions

negativly charged ions

Matter

neutral,composed of atoms

Group 1

charge +1

Group 2

charge +2

Group 3-12

lose electrons, charges can vary

Group 13

charge-3

Group 14

nonmetals: charge-4

metals: charge +4

Group 15

nonmetals: charge-3

metals: charge+5

Group 16

charge -2

Group 17

charge -1

Group 18

no charge

Isotope

atoms with the same number of protons but different numbers of neutrons

Mass number

A

sum of the number of neutrons and protons in an atom

Atomic mass number

Z

the number of protons in an atom

Isotopic symbol

A/Z X

What characteristic of an atom identifies it is an element?

the number of protons present in the nucleus (atomic number Z)

The percent natural abundance of an isotope

the relative amount of the isotope in a naturally occurring sample of the element

Valence electrons

farthest away from the nucleus

Oxidation

lose of electrons

Reduction

gain of electrons

If you gain electrons..

the charge becomes more negative

Who discovered the electron?

Thomson

Group 1

Alkali Metals

Alkali Metals

most reactive metals, violently react with water

Group 2

Alkaline Earth Metals

Alkaline Earth Metals

reactive metals but not violently

Groups 3-12

Transition Metals/elements