ATOMSInside Out

AtomThe smallest particle of an element that retains the

properties of that element.

BEC

Changes in State

Changes in State

Changes in State

Large Hadron Collider

Atom• An atom has three parts:• Proton = positive• Neutron = no charge• Electron = negative• The proton & neutron are

found in the center of the atom, a place called the nucleus.

• The electrons orbit the nucleus.

Atomic number

• Is the number of protons in the nucleus of the atom of an element

Atomic mass

• The total number of protons and neutrons in the nucleus

Atomic Weight and Isotopes

• Isotopes• Atoms of the same element that have the

same number of protons, but vary in number of neutrons

• Atomic weight• Close to mass number of most abundant

isotope

• Atomic weight reflects natural isotope variation

How many protons, electrons, and neutrons are in the following atoms?Atomic number

Atomic mass

Beryllium (Be)

4 9

Neon (Ne)

10 20

Sodium (Na)

11 23

Protons Electrons Neutrons

4 4 5 10 10 10

11 11 12

Terms

• Isotopes = atoms of a given element that differ in mass number– Isotopes have the same number of

_____________.– Isotopes differ in the number of _______.

Isotopes

• All atoms of an element have the SAME number of protons (p+)

• The p+ number is the atomic number (Z)– This is a constant– For example: All Sodium (Na) atoms have 11 p+

– If an atom loses a proton, it becomes a different element

• If Na loses 1 p+, then it has become Neon (Ne)

Z = atomic number = p+

• The number of protons identifies the atom and which element it is

• In a stable atom:– # p+ = # n0 = # e-

– Thus, Na in its stable form has 11 p+; 11 n0; and 11 e-

– If it has an unequal number of p+ and n0, then it is called an ISOTOPE

• Theoretically – an element can have as many isotopes of itself as it has neutrons, or it can add an unlimited number of n0

• For example: H has 3; C has 16; Al has 25– These can be looked up in the CRC (the

Chemistry/Physics Data Bible) or on the internet– Remember – a change in the number of n0 does

not change the element’s atom – only a change in the number of protons can do that!

The Carbon Isotope

Ions• Ions are when an atom has an unequal

number of p+ and e-

• Remember – a stable atom has a neutral overall charge due its equal number of p+ and e-

• When an atom loses or gains an e-, its charge changes accordingly– Loss of e- means a + charge; gaining an e- means a

– charge for the atom

Losing or Gaining e- . . . . .• If an atom loses an e-, then it has more p+ than

e- and it will have an overall positive charge• Different elements’ atoms can lose 1, 2, 3, or

even 4 electrons depending on various factors• If an atom has LOST e-, then it is called a

CATION or a positive ion– A Cation would be written as Al+ (the one being

understood) or Al+3

• Atoms can also gain electrons• If an atom gains electrons (from 1 up to 4), then it

will have more e- than p+ and will end up having an overall negative charge

• A negatively charged ion is called an ANION

– The element is shown this like: Na- (the 1 is understood) or Na-2

• The losing or gaining of electrons determines what type of bonds the atoms will form, and which atoms will bond to others

Ions

• Na atom_____ protons _____ electrons

• Na+ ion _____ protons _____ electrons

Name of ion: sodium ion

Ions

• Calcium atom_____ protons _____ electrons

• Ca 2+ ion _____ protons _____ electrons

Name of ion: calcium ion

Ions

• Sulfur atom_____ protons _____ electrons

• S2- ion _____ protons _____ electrons

Name of ion: sulfide ion

Ion Charge and the Periodic Table

Group # Ion Charge # e- lost/gained

I A 1+ 1 e- lost

II A 2+ 2 e- lost

III A metals 3+ 3 e- lost

V A nonmetals 3- 3 e- gained

VI A nonmetals 2- 2 e- gained

VII A 1- 1 e- gained

Naming Ions

• Name of a monatomic cation is the name of the element– Examples:

• Ca 2+ calcium ion• Al 3+ aluminum ion• K+

Naming Ions

• Monatomic anions are named by changing end of the name of the element to “ide”

Example: S2- sulfide ion

Naming Ions

• You need to know:N3- nitride ionP3- phosphide ionO2- oxide ionS2- sulfide ionF- fluoride ionCl - chloride ionBr- bromide ionI- iodide ion