The AtomChapter 2

Element

•An element is a pure substance that cannot

be broken down into simpler substances by

a chemical reaction.

••Each element is identified by a one- or

two-letter symbol.

••Elements are arranged in the periodic table.

••The position of an element in the periodic

table tells us much about its chemical

properties

Element Symbols

Most element symbols are derived from the first one or two letters of element name,

11 elements have symbols derived from Latin or German origins

Elements and Symbols

• C = Carbon

• N = Nitrogen

• O = Oxygen

• Cl = Chlorine

• Ba = Barium

• U = ?

• Mg =

• B = ?

• Ti = ?

• Zn = ?

Unusual Element Symbol

Antimony Sb stibium

Copper Cu cuprum

Gold Au aurum

Iron Fe ferrum

Lead Pb plumbum

Mercury Hg hydrargyrum

Potassium K Kalium

Silver Ag argentum

Sodium Na natrium

Tin Sn stannum

Tungsten W wolfram

• Atom: basic unit of matter

– Smallest unit of matter that individually retains the chemical characteristics of an element

– Consists of a dense central region, called a nucleus, surrounded by a negatively charged cloud

– Contains three types of subatomic particles:

• Proton

• Neutron

• Electron

The Proton

• Charge = + 1.602×10−19 C

– Called “+1” for clarity

• Located in nucleus of atom

• Mass = 1.672 x 10–24 g

– Approx. 1 unified atomic mass unit (u)

– 1 u = 1.66 x 10–24 g

• 1/12 the weight of a Carbon-12 atom

The Neutron

• No charge (0 C)

• Located in nucleus

• Mass = 1.675 x 10–24 g

– Approx. = 1 u

The Electron

• Charge = –1.602 x 10–19 C

– Called “–1”

• Located outside nucleus in an e-

“cloud”

• Mass = 9.109 x 10-28g

– Approx. = 0 u

Plum Pudding Model

• J.J. Thomson

• 1904

Gold Foil Experiment

• Ernest Rutherford

• 1909

• Proved J.J. Thomson’s theory wrong

• Evidence for existence of protons

Evidence of Electrons

Dmitri Mendeleev

(1834-1907)

• Russian chemist

– Arranged elements in horizontal rows in order of increasing atomic weight

– Started new rows in order to make columns of chemicals with similar characteristics

– Left spaces open for elements yet to be discovered

Classification of the Periodic Table

Classification by Physical Properties

Metals• Shiny

• Conduct electricity

• Ductile

– Can be drawn through wires

• Malleable (Shapeable)

• High M.P. & B.P

• Solids @ room temp

• Except Hg

Non-Metals

• Don’t tend to conduct

well

• Not usually ductile

• Tend to be brittle

• Low M.P. & B.P.

• Many are gases at r.t.

Metalloids

• Have chemical characteristics in between those of metals and non-metals

• Includes elements: B (Boron), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po), Astatine (At)

Classification by Electronic Properties

Alkali Metals

• Group 1 (1A)

• Li, Na, K etc.

• Soft, shiny metals

• Conduct heat and electricity

• React violently with H2O

– Form H2(g) and alkaline (basic) solutions

Akali(ne) Earth Metals

• Group 2 (2A)

• Be, Mg, Ca etc.

• Not as reactive as Alkali Metals, but still quite reactive

• Tend to make basic solutions when placed in water

Transition

Metals • Groups 3-12

• Tend to have high

densities and B.P.

• All are metals

• Often used for

electrical conduction

• Often have vivid

colors when in

solution

– Used for pigments

Colors of Transition Metal Compounds

IronCobalt Nickel Copper Zinc

Lanthanides

• Elements 57-71

– Lanthanum (La) to

Lutetium (Lu)

• Commonly used in lasers

• Can deflect UV and infrared

rays

Actinides/Actinoids

• Elements 89-103

– Actinium (Ac) to Lawrencium (Lr)

• Only Actinium, Thorium (Th), and Uranium (U) occur naturally

– Others created by neutron bombardment

• Radioactive

Groups 13(3A) – 16(6A)

• No common name

• Boundary between metals and non-metals

occurs here

• Contain elements abundant in earth’s crust,

atmosphere, and living things

• Contains the metalloids

Halogens

• Group 17 (7A)

• Love to form salts

with metals

– NaCl, KBr, CaCl2

• Like to form

diatomic molecules

– F2, Cl2, Br2

Noble Gases

• Group 18 (8A)

• Very unreactive

• Don’t like to bond to other molecules

• Generally not abundant

Diatomic Molecules

• Molecules consisting of only two atoms of either the same or different elements

– O2

– CO

• Homonuclear Diatomic Molecule: a molecule made of two atoms of the same element

– H2

• Heteronuclear Diatomic Molecule: a molecule made of two atoms that are different elements

– NO

Dinitrogen (N2)

Allotropism

• The existence of multiple pure forms of an element, in the same phase (solid, liquid, or gas), that differ in structure

• Different forms are called allotropes

• Can exhibit varied physical properties and chemical behaviors

• Don’t confuse allotropes with isotopes!!!

O2 O3

• Which atom does

the picture below

represent?

Atomic #

– # of protons

Atomic symbol

Atomic Mass

Atomic Weight

Mass #

Molar Mass

H C Fe Pd W

Number of

Protons

Number of

Electrons

Number of

Neutrons

Identify the atomic mass, number of protons, and number

of neutrons for the following elements.

Isotopes

• Atoms of the same element that have

different atomic masses

– Same number of protons

– Different # of neutrons

Problems

1) Lithium has two natural isotopes, 6Li and 7Li, which have percent abundances of 7.5%

and 92.5% respectively. What is the average

atomic mass of Lithium?

2) Using the percent abundances below, calculate the average atomic mass for

Carbon

a) C-12 = 98.890%

b) C-13 = 1.110%

c) C-14 = 0.0000000001%

3) Antimony (Sb) has two stable isotopes, 121Sb and 123Sb with masses of

120.9038 u and 122.9042 u, respectively. Calculate the percent abundances

of these two isotopes

Atomic Orbitals and

Electron Configurations

Atomic Orbitals

• Orbital: a specific region in an atom

thought to posses the highest probability of

containing the electron in question at any

one time

– Only hold maximum of two electrons at a time

– 4 basic types: s, p, d, f

S orbitals

• Spherical shape

• Lowest energy of the orbitals

P Orbitals

• Higher energy than s orbitals

• Dumb bell shaped

• Come in 3’s

• px, py, pz

D Orbitals

• Higher energy than s and p

orbitals

• Double dumb bell shape or

single dumb bell with a donut

• Come in 5’s

• dxy, dxz, dyz, dx2-y2, dz2

F Orbitals

• Higher energy than s, p, and d

• Come in 7’s

• How do we know where our electrons are?

• Electrons will seek the lowest E orbital available first

Hydrogen

Helium

1

Lithium?

Pauli Exclusion Principle: orbitals may hold up to

two electrons. The electrons must be of opposite spin

Hund’s Rule: electrons pair only after each orbital of equal energy

is occupied by a single electron

Problems

• Determine the electron configurations for the following atoms

1) N

2) O

3) Ne

4) Na

5) Mg

6) Al

7) S

8) Fe

9) W

Noble Gas Abbreviation

• The electron configuration of the noble gas

that precedes the element in question is

represented by the noble gas’ bracketed

symbol

– Example: C = 1s22s22p2 = [He] 2s22p2

• Write the electron configurations for

Vanadium and Bismuth

Exceptions to the Rules

• Cr

• Cu

Review Problems1) Which of the following is considered qualitative data and which is

quantitative?

a) Temperature

b) Creepiness

2) Juan likes to drive fast. If he regularly speeds along at 160 km/hr, how

quickly is he going in miles/hr? In in/s?

3) You have a box that emits a wave that has a wavelength of 5.0 x 10-7 m. Using the

electromagnetic spectrum below, predict what comes out of this box.

4) In the Macy's Thanksgiving day parade,

2009, a Smurf made his debut. His white

cap contained 36,763 L of helium and it

was about 1/10 of his body size. Using this

information, calculate the volume of the

entire float. If the density of helium

is 0.000178 g/cm3, what is the mass of the

helium for the entire float in kg?

5) Identify which of the following are heterogeneous mixtures and which are

homogeneous mixtures (solutions)

a) Jim Beam

b) Orange juice

c) Chicken noodle soup

d) 7 up (fresh)

e) Blood

f) Clorox bleach

6) What are the electron configuration and orbital box diagram for Phosphorous?

7) Which element has the chemical symbol Ag?

8) What are the electron configuration and orbital box diagram for Ag?