Download Science notes on Atoms, Periodic table

Science notes on Atoms, Periodic table
Combustion
When we burn sugar in our body it is called cellular respiration. When we burn it quickly it is
called combustion. The 3 things that are needed for combustion are:
1. Fuel
2. Oxygen
3. Heat
(^this is also called the circle of fire)
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The oxygen can be replaced with something that acts like oxygen, hence it does not
necessary mean that it HAS to be oxygen, this is why its called the oxidizing agent.
The fuel can be sugar, gas, oil etc …anything that can react with oxygen, usually it has a
lot of carbon
The heat is needed to get the reaction going. (ignition temperature)
During combustion, energy is always released
The Atom
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1st discovered & named by Democritus, who believed it was a small indivisible particle of
matter.
Aristotle believed that it was infinitely divisible (you could keep on cutting it forever). He
also believed that everything was composed of 5 elements: water, earth, fire, air &
aether
John Dalton then concluded that
 there must be particles of different elements.
 All the atoms of a single element are identical
 All atoms of different elements are different
 Atoms combine to form compounds
Thomson discovered electrons (negatively charged particles in the atom)
Rutherford, using radiation, concluded that
 Atoms are empty
 At the center of an atom is a positively charged nucleus (protons)
 Electrons orbit around the nucleus
Periodic Table
Dmitri Mendeleev created it.
g
-number of protons: 20
-number of neutrons: 20 (40-20)
-number of electrons: 20
The # of protons= # of electrons. The # of neutrons is the atomic mass minus the # of protons.
To draw the model of an element remember that the protons and neutrons go in the center
and the electrons go on the orbitals. The first orbital can hold only 2 electrons, while every
other one can hold up to 8 electrons.
Example: Boron ( 5 protons, 5 neutrons, 5 electrons)
 Quick Diagram
Every element in the periodic table is classified in a group; metals, non-metals or metalloids.
Metals
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Found at the left side of the staircase that starts at 13
Conducts electricity & heat
Ductile & malleable
Non-Metals
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Found on the right of the staircase that starts at 13 (hydrogen is included)
Poor conductors of electricity & heat
Metalloids
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Basically includes all the elements along the staircase at 13 (boron, silicon, germanium,
arsenic, antimony, tellurium & astatine)
They have both metal & non-metal properties
Sometimes good conductors of electricity
The elements are also placed into groups based upon similar chemical reactions. All elements in
the same chemical group share similarities during chemical reactions.
The Alkali metals
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Elements along the first column except for hydrogen (lithium, potassium…)
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They are highly reactive & must be stored in oil
Are soft & malleable
The Alkali earth metals
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Elements along the second column (beryllium, magnesium, calcium…)
They are somewhat reactive but less reactive than the alkali metals
Highly malleable
Burns easily if there is heat
The Halogens
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Elements along the 7th column (fluorine, chlorine…)
Non-metal
Powerful disinfectants
React to form compounds
Noble Gases
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Elements along the 8th column (helium, neon…)
Very stable, rarely react
Colorless & odourless
“Periods” are referred to the rows in the periodic table.
Balancing Equations
To balance solutions we can’t ever change or touch the exponent attached to the element.
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NH3 + Cl2 HCl + N2 (not balanced)
 2NH3 + 3Cl26HCl+ N2 (balanced)
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NaOH Na +O2 + H2O
 12NaOH 12Na+ 3O2+ 6 H2O
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NaI + Pb(NO3)2 PbI2 + NaNO3
 NaI + PbNO6  PbI2 + NaNO3
 2 NaI + PbNO6 PbI2 + 2NaNO3 (balanced)
Lewis dot diagram
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Displays the valence electrons in an element
Valence electron means number of electrons on the outer most orbital of an element
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Valence electrons are equal to the number of the column ( ex: hydrogen has 1, carbon
has 3..)
Valence number is the amount of levels an element has and is equal to the number of
the row ( ex: lithium has 2 layers, potassium has 4…)
Covalent bonds
When a metal element & a non-metal element bond together they form iconic bonds.
Naming iconic bonds: name the element and then name the second element except end it with
an “ide”
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KBr potassium bromide
NaCo2 Sodium carbonate
NaF Sodium fluoride
Non-metals want to receive electrons whereas metals want to give away electrons. The
valence electrons of an element determines how many electrons an element wants give or
take. When the two elements bond together the exponents switch over (cross over rule)
Examples:
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Lithium is a metal, it has 1 valence electron therefore it wants to give away 1 electron.
All metals want to have 8 valence electrons. Carbon is a non-metal, it has 6 valence
electrons & it wants to have 8 therefore it takes 2 valence electrons.
Li1+ & C2-  cross over rule & becomes Li2C (lithium carbonate)
Co3+ & CO2- 3  Co2(CO3)3 (Cobalt carbon oxide)
When a non-metal element and a non-metal element bond together they form covalent bonds.
When naming covalent bonds you must include the # of the exponent. The crossover rule also
applies here.
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C2 & O  CO2 (carbon dioxide)
1=mono
2= di
3=tri
4=tetra
5=penta
6=hexa
7=hepta
8=octa
9=nona
10=deca
ex: N2O3 (dinitrogen trioxide)
Moles
1 mole of an element is basically its atomic mass. 2 moles of an element would be 2 times its
atomic mass.
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4Fe2S …its mass? 8 x atomic mass of Fe + atomic mass of S
= 8(56) + 4(32) = 576
How many moles is 100 grams of sulfur?
x= 100/32 = 5.06
How many moles is 182.305 g of HCl?
 1(H) + 35 (Cl) = 36 (so 1 gram of HCl is 36)
X= 5.06
Sometimes they give you formulas and ask you to answer specific questions. To get the answer
1. Make sure the formulas are balanced (if they aren’t balance them)
2. Create the table
3. Circle the elements that you need
4. Set up a proportion and solve to find the answer
Example:
2NaOH + H2SO4  2H2O + Na2SO4
How many grams of sodium sulfate will be formed if you start with 200 grams of sodium
hydroxide?
1. They are balanced
2.
3.
4.
80 grams of sodium hydroxide creates
142 grams of sodium sulfate, so how
many grams of sodium sulfate would be
created if there were 200 grams of sodium hydroxide?
x= 355 grams
,