Chapter 2 Flashcards
Atomic #=
Atomic #= Z (Mass # )= P^+(number of protons)
Charge=
Charge=P-e
Protons - electrons
Mass=
Mass #= A = protons + neutrons
Notation of an isotope
AZE”, notation where A is the mass number, Z is the atomic number, and E is the element symb
In neutral isotopes
Electrons are equal to protons
Percent abundance formula
(M1)(x) + (M2)(1-x) = M(E)
M1 denotes the mass of one isotope’
x denotes its relative abundance.
The mass of the second isotope is denoted by M2.
M(E) denotes the periodic table element’s atomic mass.
Atomic weight formula
(Percent abundance of isotope 1/100)(mass of isotope 1) + (percent abundance of isotope 2/ 100) (mass iso 2)
Ionic compound
Metal and non metal or polyatomic ion
Covalent
Non mental w non metal
Naming for metals
Prefixes and ide ending
Naming for transition metals
Roman numerals and ide ending or polyatomic name
Prefixes
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
Metalloids
B, Si, As, Te, Ge, Sb
Group 1 is called
Alkali metals excluding H
Group 2 is called
Alkaline earth metals
Group 17 are
Halogens
Group 18
are noble gases
Highest reactivity of elements
Bottom left (metals are more reactive as we go down)
Top right (non metals are more reactive as we go up)
Elements by ancient Greeks
Elements
• ancient Greeks believed there were four: Earth, Fire, Water, Air
Who proposed the concept of atoms
Atoms
• Democritus & Leucippos (~400 BC) proposed concept of tiny particles
Alchemy
Alchemy
• attempts to transmute “base” metals (i.e., cheap ones) into gold
• went on for about 2000 years without success…
• …but lead to discovery of many elements & chemicals (e.g., mineral acids)
Extraction of metals from minerals
Extraction of metals from minerals
• geologist Georg Bauer a.k.a. Georgius Agricola (German 1494 - 1555)
Medicinal use of minerals
Medicinal use of minerals
• Philippus Theophrastus) did this & also a lot of synthetic chemistry
What did Robert Boyle do? What did he believe?
• Robert Boyle (English, 1627 - 1691): among first to “measure” things
• did not believe in Greeks’ four elements
• his idea: an element = a substance that cannot be further broken down
• did not believe metals were elements → : he dabbled in alchemy…
Phlogiston: a major scientific dead-end (1667 - mid 1700s)
former theory of combustion in which all flammable objects were supposed to contain a substance called phlogiston, which was released when the object burned. phlogiston was presumed to have negative mass!
Who is the father of modern chemistry and what did he introduce
• Lavoisier = the father of modern chemistry
• introduced systematic terminology & quantitative experimentation
And Law of Conservation of Matter
John Dalton’s atomic theory (1803):
- All matter is made of atoms.
- All atoms of an element are identical. ‹ not exactly true…
3.A given compound always has the same relative #s & types of atoms. - Chemical reactions involve the reorganization of atoms, but the atoms themselves are not changed. except in nuclear reactions.
Marie Curie (1876-1934): atoms made of smaller particles
Discovered one of the pieces of evidence for the fact that atoms are made up of smaller particles
Radioactivity:
= the spontaneous disintegration of some elements’ accompanied by emission of unusual “rays”
J.J. Thomson (1897): electrons in all atoms
J.J. Thomson’s experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged “soup.”
J J Thompson experiments
J.J. Thomson’s cathode ray tube experiment discovered the subatomic particle the electron. Prior to the experiment, it was not known that atoms were composed of further particles. Cathode rays were determined to be composed of negatively charged particles that were smaller than the smallest atom.
Robert Millikan
In the experiment, Milliken allowed charged tiny oil droplets to pass through a hole into an electric field. By varying the strength of the electric field the charge over an oil droplet was calculated, which always came as an integral value of ‘e. ‘
Eugene Goldstein discovered what
Eugene Goldstein discovered positive particles by using a tube filled with hydrogen gas (this tube was similar to Thomson’s tube). This resulted in The positive particle had a charge equal and opposite to the electron. The positive particle was named the proton.
How do we measure masses & abundances of isotopes?
using a mass spectrometer
Mass spectrometer how it works
Atoms ionized to form CATIONS (= positively charged ions)
- Electric field pulls cations through magnetic field
• Ions are deflected – heavy ions deflect LESS
→ IONS SEPARATED BY MASS
Isotopes
ISOTOPES = Atoms with same # protons (:: same element)
same # electrons
BUT different # neutrons (:: different mass)
Ernest Rutherford (1910): protons in nucleus
Ernest Rutherford found that the atom is mostly empty space, with nearly all of its mass concentrated in a tiny central nucleus. The nucleus is positively charged and surrounded at a great distance by the negatively charged electrons
Describe the gold foil experiment and who created it
In 1899 Ernest Rutherford studied the absorption of radioactivity by thin sheets of metal foil and found two components: alpha (a) radiation, which is absorbed by a few thousandths of a centimeter of metal foil, and beta (b) radiation, which can pass through 100 times as much foil before it was absorbed.
Metals characteristics
conduct heat & electricity
• malleable, ductile, lustrous (shiny)
• exist as atomic SOLIDS
(except for Hg = liquid)
Non metals characteristics
insulators, non-malleable
• gases, liquids, non-lustrous solids
• many exist as diatomic molecules:
Iz. H2, N2, Brz, 02, Clz, F2
“I have no bright or clever friends…
Metalloids characteristics
” some properties of both M & NM
Si: shiny but brittle, semiconducting
Period is
Horizontal
Group is
Vertical
Group 18 (8A) = noble gases: characteristics
All exist as free atoms: e.g., Kr(g)
*radioactive
• Lighter-than-air balloons: He(g)
• Neon signs: more in Ch.6
• The most unreactive elements
Group 17 (7A) = halogens: characteristics
Exist as diatomic molecules: F2(g), Cl(g), Brz(l), I2(s)
• Quite reactive: elemental forms not found in nature
• React violently with alkali metals to form ionic compounds
Group 1 (1A) = alkali metals: characteristics
Elemental form: soft silvery “atomic” metals, M(s)
All are violently reactive towards water, air &
In nature: found in compounds as M+ cations (never in elemental
Group 2(2A)=alkaline earths: characteristics
Elemental form:
•quite reactive metals
• In nature: found only in compounds, as M2+ cations e.g. in CaCO, limestone
Group 15 pnictogens: characteristics
Nitrogen very unreactive
Phosphorus: highly reactive
Group 16 (6A) = chalcogens:
Oxygen: colourless gas
Sulfur:
• Quite reactive…
Family
Elements with similar chemical and physical properties VERTICAL
Groups
Tells us the reactivity and how many valence electrons for 11 and so on look at the last digit
Moles formula
N= mass in grams/ molar mass (g/mol)
Mass percent of an element formula
Mass percent=( mass of element asked/ total mass) * 100%
Empirical
All subscripts at lowest form
Molecular
All subscripts as is
Who disproved phlogiston
phlogiston theory disproved once:
• Joseph Priestly (English, 1733 - 1804) discovered oxygen
• Antoine Lavoisier (French, 1743 - 1794) added rigour & explanation
Diatomic elements
I2, H2, N2, Brz, O2, Cl2, F2
“I have no bright or clever friends…
who is dmitri mendeleev?
Argued that element properties are
periodic functions of their atomic
weights
Developed the modern periodic table.
We NOW know that element properties
are periodic functions
of their ATOMIC NUMBERS
periods are organized in
rows (from left to right)
groups are organized by
up and down as families
IUPAC 1-18
Metal
conduct heat & electricity
malleable, ductile, lustrous (shiny)
exist as atomic SOLIDS
(except for Hg = liquid)
Non metal
insulators, non-malleable
gases, liquids, non-lustrous solids
many exist as diatomic molecules:
I
2, H
2, N
2, Br
2, O
2, Cl
2, F
2
“I have
no bright
or clever
friends…”
Metalloid
some properties of both M & NM
Si: shiny but brittle, semiconducting
First 20 elements
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminium
Silicon
Phosphorus
Sulphur
Chlorine
Argon
Potassium
Calcium
Where are the most reactive elements found?
the most reactive elements at left & right
edges of table (ignoring noble gases)
Do metals lose or gain?
Metals lose electrons
When are metals the most reactive?
more reactive as go down group
(larger atoms lose e
-s more easily
What is 1A called?
Alkali metals excluding hydrogen
What is group 2A called?
Alkaline earth metals
Whats the last group called?
Noble gases
What is the middle group called?
Transition metals
What are the before last group called?
Halogens
Group 18 characteristics
All exist as free atoms: e.g., Kr(g)
Lighter-than-air balloons: He(g)
Neon signs: more in Ch.6
The most unreactive elements
(although… heavy ones can be forced
to react with very reactive substances
to form compounds
Group 17 characteristics
Exist as diatomic molecules: F2(g), Cl2(g), Br2(l), I2(s)
Quite reactive: elemental forms not found in nature
React violently with alkali metals to form ionic compounds
Group 1A characteristics
Soft silvery atomic metals
React violently towards water, air and halogens
Found in compounds in nature never elemental form
Group 2A
Elemental form:
* quite reactive metals
In nature: found only in
compounds, as M2+ cations
e.g. in CaCO3 limestone
Hydrogen
Exists as H2, highly combustible, in most reactions, forms H+ ions like alkali metals do and in some reactions forms H- ions like halogens do
Charge of electrons
1-
Charge of proton
1+
Charge of neutron
0
