Cehm Flashcards
bring together elements with similar properties.
The vertical groups
are arranged in order of increasing atomic number from left to right. The groups are numbered at the top. and the periods at the extreme left in the periodic table on the inside front cover.
The horizontal periods
The first two groups
the s block-
the last six groups
the p block
together constitute the main-group elements
S block and p block
are known as the transition elements.
The d-block elements
The f-block elements
sometimes called the innertransition elements
sometimes called the innertransition elements
The f-block
the f-block elements are extracted from the table and placed at the bottom
The 14 elements following lanthanum (Z = 57) are called
lanthanides
actinium
actinides.
Have a shiny luster various colors,
although most are silvery
Solids are malleable and ductile
Good conductors of heat and electricity
Mest metal oxides ave ionic solids that
are basic
Tend to for cations in aqueous solution
Metals
Donot have a luster: various colors
Salids are usuallvbrittle: some are hard.
and some are soft
Poor conductors of heat and electricity Mest nonmetallic oxides are molecular
substences that formacid ic solutions
Tend to form anions or orvanions in
aqueous solution
Nonmetals
are elements that look like metals and in some ways behave like metals, but also have some nonmetallic properties.
Metalloids
Atomic Properties and Periodic Table
●Atomic size
●Metallic and Non-metallic character
●Ionization (energy) potential
●Electron affinity
●Electronegativity
As we increase the atomic number (or go down a group). . .
•each atom has another energy level,
•so the atoms get bigger.
Atomic Size
Atomic Size - Period Trends
Going from left to right across a period, the size gets smaller.
•Electrons are in the same energy level.
•But, there is more nuclear charge.
•Outermost electrons are pulled closer
is the tendency of an element to lose electrons and form positive ions (cations). For e.g., alkali metals are the most electropositive elements.
It is also known as electropositivity.
Metallic character
The tendency of an element to accept electrons to form an anion is called
non-metallic or electronegative character
For e.g., chlorine, oxygen and phosphorous show greater electronegative or.”
non-metallic character
Trends across the period
Metallic character of elements decreases as we move to the right.
●Elements to the left have a pronounced metallic character while those to the right have a non-metallic character.
●Non-metallic character increases from left to right.
Why does the metallic character decrease from left to right across the period?
The elements to the left of the periodic table have a tendency of losing electrons easily as compared to those to the right.
➢As we move from left to right of the period, the electrons of the outer shell experience greater pull of the nucleus.
➢This greater force of attraction is because the nuclear charge increases and the size of the atom decreases from left to right.
Why does metallic character increase down the group?
●As we move down the group the number of shells increases.
●This causes the effective nuclear charge to decrease due to the outer shells being further away: in effect the atomic size increases.
●The electrons of the outermost shell experience less nuclear attraction and so can lose electrons easily thus showing increased metallic character.
The amount of energy required to remove the most loosely bound electron from an isolated gaseous atom is called ionization energy (IE).
It is measured in the units of electron volts (eV) per atom or kilo joules per mole of atoms (kJ mol-1).
Ionization energy (IE).
The ionization energy increases with increasing atomic number in a period.
The ionization energy increases with increasing atomic number in a period.
This is because
●The nuclear charge increases on moving across a period from left to right.
●The atomic size decreases along a period though the main energy level remains the same.
●Due to the increased nuclear charge and simultaneous decrease in atomic size, the valence electrons are more tightly held by the nucleus.
Therefore
more energy is needed to remove the electron and hence ionization energy keeps increasing.
Variation down a group
●The ionization energy gradually decreases in moving from top to bottom in a group.
This is due to the fact that:
●The nuclear charge increases in going from top to bottom in a group.
●An increase in the atomic size due to an additional energy shell (level) ‘n’.
As a result ,
the electron becomes less firmly held to the nucleus and so the ionization energy decreases as we move down the group.
is the amount of energy released when an electron is added to an isolated gaseous atom.
Electron affinity
This the relative tendency of an atom in a molecule to attract a shared pair of electrons towards itself
Electronegativity
The value of electronegativity of an element describes the ability of its atom to compete for electrons with the other atom to which it is bonded.
had the idea that all matter consisted of minute particles, which he the coined as “atomos.” However, his idea about atoms was not accepted by the community because he could not provide factual basis to his claims because it was purely based in philosophical reasoning.
Democritus
(1803) an English school teacher, gave the first atomic Theory who provide precise and detailed description of the building blocks of matter
John Dalton
is the smallest particle of an element that has the chemical characteristic of that element.
ATOM
All matter is composed of elements.
•All the atoms of a given elements are same or identical.
•The atoms of different elements have different masses.
•A compound is a specific combination of atoms of more than one element
•In a chemical reaction, atoms are neither created nor destroyed but are merely rearranged to produce new substances.
John Dalton’s Atomic Theory
Atoms may be disintegrated by
transmutation process.
(Transmutation is a process in which atom is converted either the complex or disintegrated atom.)
•Not all atoms of a given element are identical or the same
•Not all atoms of a given element have identical characteristics except mass.
•Atoms of different elements have different
Modern Atomic Theory
Electrons
Joseph Thomson
In 1897, British physicist —— investigated the “cathode rays” that emitted rays when high voltage is applied between two electrons in a glass tube containing small amount of gas. His observation confirmed the earlier work, suggesting that a stream of particles move from one
Joseph Thomson
emitted rays when high voltage is applied between two electrons in a glass tube containing small amount of gas
cathode rays
Thomson discovered that the properties of rays were the same no matter what metal is used for the electrodes. Thomson showed that cathode rays are stream of negatively charged particles coming from the inside of the atoms that made up of the cathodes — these particles are called electrons. He also measured the value of e/m, which is the ratio of the size of electron’s charge to its mass and found it to be ?????
1.76 x108 Coulomb/gram.
an American, found that
e = 1.6 x 10-19 C based on his oil drop experiment. Therefore, the mass of electrons (e) will be:
Mass of electron = e x m/e
= 1.6 x 10-19 C x 1/1.76 x108 Coulomb/gram
Robert Millikan
is the positively charged subatomic particle with a mass of 1.6726 x 10-24g. It is located at the center of the atom called the nucleus. It was discovered by Ernest Rutherford, a New Zealander, using the gold foil experiment.
Proton
Proton
Ernest Rutherford
gold foil
Ernest Rutherford
neutral subatomic particle with a mass of 1.6749 x 10-24 g
neutron
neutron
James Chadwick
Beryllium foil experiment.
James Chadwick
He proposed that the electrons in an atom could only be in a certain orbits, or energy levels, around the nucleus; that is his theory was that the energy of the electrons is quantized and can only be lost or gained in discrete amount.
This theory led to the modern theory of atomic
Niels Bohr
British scientist, was the first to measure the atomic number accurately.
Henry Moseley
equal to the number of protons in an atom
The atomic number (Z) is
•To calculate for e-, p+ and n0.
A – Z = neutron
Z = proton
Z = electron (if element is uncharged)
Z – c = electron (if element is charged)
n0 + p+ = mass number (A)
One atomic mass unit is 1/12 the mass of an atom of Carbon-12. The mass of a single carbon-12 atom is 1.9926 x 10-23 g = 1.6605x10-24 g.
1 u = 1.9926 x 10-23 g = 1.6605x10-24 g
12
are atoms that have the same atomic number but different atomic mass
Isotopes
are isotopes that do not undergo radioactivity and do not disintegrate; thus they are abundant in nature
Stable isotopes
are those that exhibit radioactivity and can be artificial or natural. Nevertheless, both emit radiation in the form of alpha, beta and gamma rays
Unstable isotopes
consolidated average of the masses of the naturally existing isotopes relative to the mass of Carbon-12.
Isotopic abundance or Relative Atomic Mass
i’m Mass number = Σ (% Abundance) (mass of the isotope)
represents a compound in terms of chemical symbols; it indicates the elements and numbers of atoms present in a compound.
-In writing the formula of a compound, always consider the rule that the total positive charges must be equal to the sum of the total negative charges. Therefore the compound must have a net zero charge.
Chemical Formula
should be written first followed by the negative ion.
The positive
The net ionic charge of the positive ion and the negative ion is equal to zero.
The net ionic charge of the positive ion and the negative ion is equal to zero.
Na+ and Cl- Na+1 + Cl-1 = NaCl (0)
H+ and S-2 H+1+ S-2 = H2S (0)
Mg+2 and Br- Mg+2 + Br-1 = MgBr2
The shortcut method to get the correct formula of a binary compound is to write each ion with its charge. You should start with the positive ion then cross over the number (not the plus or minus sign) and write them as subscripts.
consist only of two elements
Binary compounds
Metal + non-metal
the name of the positive element (metals) is written first followed by the name of negative element (non-metal) with the ending –ide.
the name of the positive element (metals) is written first followed by the name of negative element (non-metal) with the ending –ide.
Al2S3 Aluminum sulfide
Mg3N2 Magnesium nitride
KCl Potassium chloride
Na2O Sodium oxide
VARIABLE OXIDATION NUMBER
a) Stock System or Roman Numeral System
•metallic elements written first followed by its oxidation number in Roman Numeral enclosed in parenthesis:
Fe+3 + O-2 Fe2O3 Iron (III) oxide
Hg+2 + Cl-1 HgCl2 Mercury (II) chloride
Cu+2 + Br-1 CuBr2 Copper (II) bromide
VARIABLE OXIDATION NUMBER
b) Classical or Conventional System
In this method the suffix “ous” is added to the Latin name of the electropositive metal with a lower oxidation state and the suffix “ic” applied with the higher oxidation state.
FeCl2 Ferrous chloride SnF2 Stannous fluoride
FeCl3 Ferric chloride SnF4 Stannic fluoride
NAMING BINARY
NAMING BINARY COMPOUNDS
Common Cations with variable oxidation numbers
Au+1 Aurous or gold (I)
Au+3 Auric or gold (III)
Co+2 Cobaltous or cobalt (II)
Co+3 Cobaltic or cobalt (III)
Cu+1 Cuprous or copper (I)
Cu+2 Cupric or copper (II)
Fe+2 Ferrous or Iron (II)
Fe+3 Ferric or Iron (III)
NAMING BINARY COMPOUNDS
Common Cations with variable oxidation numbers
Pb+2 Plumbous or Lead (II)
Pb+4 Plumbic or Lead (IV)
Mn+2 Manganous or Manganese (II)
Mn+3 Manganic or manganese (III)
Hg2+2 Mercurous or mercury (I)
Hg+2 Mercuric or mercury (II)
Sn+2 Stannous or Tin (II)
Sn+4 Stannic or Tin (IV)
NAMING BINARY COMPOUNDS
3. In naming binary compounds containing two non-metals, the rule is similar to naming ionic compounds except that prefixes are used.
compounds which is composed of hydrogen and a more electronegative element is named in the same as binary compound of nonmetal.
-The word hydrogen is named first followed by the second element which is made by affixing the suffix –ide to the root word of the nonmetal.
HCl Hydrogen chloride
HF Hydrogen fluoride
HBr Hydrogen bromide
When the above substances are dissolved in water, they become aqueous acids. In these acids the prefix “hydro” is attached to the root word of the nonmetal and the suffix -ic is added followed by the word acid.
HCl(aq) Hydrochloric acid
HF(aq) Hydrofluoric acid
HBr(aq) Hydrobromic acid
HI(aq) Hydroiodic acid
H2S(aq) Hydrosulfuric acid
Polyatomic compounds are formed in the same way as binary compounds. A polyatomic ion is a stable group of atoms that carries an overall electrical charge.
- In naming compounds containing polyatomic ions the positive ion should be written first followed by the negative ion. However, parenthesis is placed around the polyatomic ion and the subscript is written just after the close parenthesis whenever a multiple of the polyatomic ion is necessary.K2CrO4 Potassium chromate
Zn(NO2)2 Zinc nitrite
Fe2(SO4)3 Ferric sulfate
Mg3(PO4)2 Magnesium phosphate
NaHCO3 Sodium bicarbonate
another polyatomic compounds are compounds made up of hydrogen, oxygen and another elements. Suffix is used to differentiate the non-metals between two ternary oxyacids. The name of the acid containing the non-metal with the lower oxidation number is “ous”. The name of the acid containing a nonmetal with the higher oxidation number carries the suffix “ic.”
TERNARY OXIDE
TERNARY OXIDE
HNO3 Nitric acid
HNO2 Nitrous acid
H3PO4 Phosphoric acid
H3PO3 Phosphorous acid
H2SO4 Sulfuric acid
H2SO3 Sulfurous acid
TERNARY OXIDE
HClO4 Perchloric acid
HClO3 Chloric acid
HClO2 Chlorous acid
HClO Hypochlorous acid
HIO4 Periodic acid
HIO3 Iodic acid
HIO2 Iodous acid
HIO Hypoiodous acid
with more than one positive ion can be formed from an acid containing two or more hydrogen atoms by placing one hydrogen or both with different metals
SALTS
is formula of the compound gives the smallest and simplest number ratio of atoms that make up the compound.
Empirical Formula (EF)
STEPS IN DETERMINING THE EF:
1.Change the percent to gram, using 100 g of compound as basis
2.Calculate the number of moles of each element
3. Divide the number of moles of each element by the smallest number of moles. If it does not result in a whole number, multiply the mole ratio by a common factor to convert these to whole number.
Example 1
Determine the empirical formula of a compound containing 74.19% Na and 25.81% O.
Calculate the empirical Formula of a compound containing 52.9% Al and 47.1% O.
Example 2
ANSWER:
EF = Al2O3
MOLECULAR FORMULA
Molecular Formula (MF)
is the true formula of the compound and shows the actual number of atoms of each element present in one molecule of a compound.
STEPS IN DETERMINING THE MF:
1.Determine the Empirical Weight (EW) of the Empirical Formula (EF).
2.Divide the given Molecular weight (MW) by the Empirical Weight to solve for the Molecular Ratio (MR). MR = MW/ EW
- Multiply the value of MR to the EF to get the Molecular Formula (MF).
MF = MR x EF
Vanillin is the active flavoring agent in vanilla bean, that contains 63.14% Carbon, 5.31% Hydrogen and 31.55% Oxygen. What is the MF of vanillin with Molecular weight of 152 g/mole?
ANSWER:
MF = C8H8O3
What is the Empirical Formula of C4H10?
ANSWER:
EF = C2H5
Which of the following is an Empirical Formula?
A. H2O2
B. P4O10
C. NO2
D. C2H4
ANSWER:
C. NO2
TO MEASURE ELEMENT
STOICHIOMETRY
Greek) meaning ELEMENT
stoichelon
Greek) meaning TO MEASURE
metron
is the sum of the atomic weights of all the atoms present in a molecule.
MOLECULAR WEIGHT
in SI system is the amount of a substance that contains as many elementary entities (atoms, molecules or other particles) as there are atoms in exactly 12 grams of the C-12 isotope.
MOLE
