General Chemistry Unit 2 Atomic Structure

ElEmEnts numbErs 1-20

Hydrogen

Symbol- H Gas

Helium

Symbol- He Gas

Lithium

Symbol- Li Solid- metal

Beryllium

Symbol- Be Solid

Boron

Symbol- B Solid

Carbon

Symbol- C Solid

Nitrogen

Symbol- N Gas

Oxygen

Symbol- O Gas

Fluorine

Symbol- F Gas

Neon

Symbol- Ne Gas

Sodium

Symbol- Na Symbol from natrium,

Latin word for sodium carbonate.

Solid

Magnesium

Symbol- Mg Solid

Aluminum

Symbol- Al Solid

Silicon

Symbol- Si Solid

Phosphorus

Symbol- P Solid

Sulfur

Symbol- S Solid

Chlorine

Symbol- Cl Gas

Argon

Symbol- Ar Gas

Potassium

Symbol- K Name from

Kalium, Latin word for alkali

Solid

Calcium

Symbol- Ca Solid

Atomic Structure

Atoms (Elements)

Are made up of 3 parts: Protons Neutrons Electrons

Protons, Neutrons, Electrons

Protons positively charged found in nucleus

Neutrons neutral subatomic particles found in the nucleus

Electrons negatively charged found outside the nucleus

Zoom In…

Atomic Number

Atomic Mass

Atomic and Mass Number

Atomic Number The number of PROTONS in the nucleus of the atom The atomic number identifies the element

Atoms are electrically neutral

# of PROTONS = # of ELECTRONS

Mass Number The total number of PROTONS and NEUTRONS in

the nucleus of an atom

SAMPLE PROBLEMS

How many protons, neutrons and electrons are in an atom of Be-4? Protons = 4 Electrons = 4 Neutrons = 5

How many protons, neutrons and electrons are in an atom of Ne – 10 Protons= 10 Electrons= 10 Neutrons= 10

ElEmEnts sEcond 20

Copper

Symbol- Cu

Silver

Symbol - Ag

Gold

Symbol- Au

Tin

Symbol- Sn

Strontium

Symbol- Sr

Cesium

Symbol- Cs

Rubidium

Symbol- Rb

Barium

Symbol- Ba

Bromine

Symbol- Br

Iodine

Symbol- I

Nickel

Symbol- Ni

Mercury

Symbol- Hg

Iron

Symbol- Fe

Lead

Symbol- Pb

Zinc

Symbol- Zn

Uranium

Symbol- U

Cobalt

Symbol- Co

Selenium

Symbol- Se

Platinum

Symbol- Pt

Chromium

Symbol- Cr

Ions

valence electrons- are the electrons in the last shell or energy level of an atom Can determine by looking at the periodic table

Valence Electrons

What is the appropriate number of valence electrons for the following elements: H

P

F

Ar

C

Practice: Valence Electrons

~ 1

~ 5

~ 7

~ 8

~ 4

Atoms want to have 8 valence electrons- happy But not all elements have 8 valence

electrons… Therefore some atoms become ions…

Valence Electrons

Ion- an atom or group of atoms that have a positive or negative charge An ion has either gained or lost electrons Examples: Na+1 Ca+2 I-1 O-2

Na Ca I O

Cation- positive ion has lost electron(s) Anion- negative ion has gained electron(s)

Ions

Predicting Ion Charges

In general metals (Mg) lose electrons ---> cations nonmetals (F) gain electrons ---> anions

-1 -2 -3 +1

+2

By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.

+3

Charges on Common Ions

Guess the charge for the following elements:

Mg

K

F

N

Guess the Charge

Mg +2

K +1

F -1

N -3

State the number of protons, neutrons, and electrons

in each of these ions.

Let’s Practice

Protons Neutrons Electrons

39 K+

19 16 O -2

8 41 Ca+2

20

Mass #

Atomic #

Isotopes

Isotopes

Isotope- an atom that has the same number of protons as another atom but a different number of neutrons

Isotopes of chlorine

35Cl 37Cl 17 17

Isotopes

To distinguish between isotopes, look at mass numbers

Isotopes of chlorine

35Cl 37Cl 17 17

chlorine - 35 chlorine - 37

Some Isotope Examples Hydrogen

1H- Hydrogen

1

2H- Deuterium

1

3H- Tritium

1 Carbon

12C

6 14C

6

Practice Naturally occurring carbon consists of three isotopes, 12C,

13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.

Protons Neutrons Electrons 12C 6 13C 6 14C 6