Download The Atom Chapter 2

The Atom
Chapter 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
Copper
Gold
Iron
Lead
Mercury
Potassium
Silver
Sodium
Tin
Tungsten
Sb
Cu
Au
Fe
Pb
Hg
K
Ag
Na
Sn
W
stibium
cuprum
aurum
ferrum
plumbum
hydrargyrum
Kalium
argentum
natrium
stannum
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 Carbon12 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 nonmetals
• 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
Iron
Cobalt
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
Dinitrogen (N2)
• 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
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
Number of
Protons
Number of
Electrons
Number of
Neutrons
C
Fe
Pd
W
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
1
Helium
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)
2)
3)
4)
5)
6)
7)
8)
9)
N
O
Ne
Na
Mg
Al
S
Fe
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 Problems
1)
2)
Which of the following is considered qualitative data and which is
quantitative?
a)
Temperature
b) Creepiness
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?