Transcript Covalent Bon

Unit 1
Revision
Chapter 2 - 8
Chapter 2 – A particle view of matter
What you should be able
to do:
• Describe the structure of
the atom in terms of the
arrangement of protons,
neutrons and electrons
• Isotopes
– Calculate abundance and
Relative Atomic Mass
• Electron configuration
– Excited and ground state
Atomic Theory
• Explains the structure of atoms
• Atoms are made up from sub-atomic particles.
• Protons – found in the nucleus and have a positive
charge. Relative mass of 1
• Neutrons – found in the nucleus and have no charge.
Relative mass of 1
• Electrons – orbit the nucleus in specific energy levels
known as shells – take up most of the space occupied
by an atom. Relative mass of 0.0005
Structure of the atom
Protons:Found in nucleus
Positive charge (+ve)
Mass = 1
Number of protons is
known as the Atomic
number.
Each element has a
different number of
protons.
Protons are made form
quarks and gluons.
Neutrons:Found in nucleus
No charge
Mass = 1
Neutrons act to stabilise
the nucleus and hold the
protons together with
the strong force.
The Relative atomic
mass is the number of
protons + number of
neutrons.
Neutrons are made form
quarks and gluons.
Electrons:Found in (orbits) shells around the nucleus.
Each shell and sub-shell represent a particular energy
level that the electrons are found at. These energy levels
can be explained by quantum mechanics.
The number of electrons equals the number of protons unless
the atom forms an ion.
Isotopes
• Most elements form isotopes
• An Isotope is an element that has atoms that
have a different number of neutrons.
• The RAM on the periodic table is an average for
that element taking into account the abundance of
Mass Spectrometer
the isotopes for that element.
• Isotope calculations are an important part of
chemistry. Page 38 of your text gives you the
formula and an example of these types of
calculations.
• A mass spectrometer can be used to detect the
presence and number of isotopes present in a
sample of an element.
Mass spectrum of
Bromine molecules
Shells and Sub Shells
Chapter 3 – The periodic table
What you should be
able to do:
• Explain the periodic
variation of
elements
• Locate an element
on the periodic
table given electron
configuration
Chapter 4 – Relative Atomic Mass and
the Mole
What you should be
able to do:
• Calculate Relative
Atomic Mass from
isotopes and mass
spectrometers
• n=m/M
• N=n x NA
• Calculate % by mass
• Determine empirical
formula
• Determine molecular
mass
Mole calculations
n= m
M
Number of mol = mass of chemical in grams
divided by its Molar Mass.
m=nxM
Mass of a chemical in grams = number of mol x
Molar mass.
M= m
n
Molar Mass of unknown chemical = mass in
grams ÷ number of mole
Particles = n x NA
n = Particles
NA
Particles present = number of mole x
Avogadro's number.
Number of mole = Particles present ÷
Avogadro’s Number.
Percentage composition
• Percentage composition tells us the amount
by mass of each element present in a
compound.
Molar mass = (39.1 x 2) + (52 x 2) + (16 x 7)
= 294.2 gmol-1
% Oxygen = (16 x 7) x 100
294.2
1
= 38%
Empirical formula
• The simplest whole number ratio of atoms
present in a compound.
• H2O
C2H3O4
C6H12O6
• You must be able to perform calculations to
determine empirical formula.
Molecular formula
• The molecular formula is the actual formula of a
chemical which is not always in its simplest form
(empirical formula)
To calculate the Molecular Formula:
Molecular formula mass / empirical formula mass =
the number of times the empirical formula
Practice Exam Questions
Which of the following atoms is in its
ground state?
A. 1s22s23s2
B. 1s22s22p5
C. 1s22s22p63s24s1
D. 1s22s22p63s23p63d54s2
Practice Exam Questions
The element that can be found in group
2 period 4 of the Periodic Table is:
A. Mg
B. Ca
C. Sr
D. Ba
Practice Exam Questions
The percentage by mass of uranium in
uranium oxide (U3O8) is:
A. 84.8%
B. 82.3%
C. 80.1%
D. 88.5%
Practice Exam Questions
The mass of 0.25 mol of aluminium
oxide (Al2O3) is:
A. 20.45g
B. 25.23g
C. 25.50g
D. 22.19g
Practice Exam Questions
The empirical formula of the compound
with the composition: 42.9% carbon
and 57.1% oxygen is:
A. CO2
B. C2O2
C. CO
D. C2O
Practice Exam Questions
Which of the following atoms has the
greatest number of neutrons?
A. 57Co
B. 58Fe
C. 56Mn
D. 56Ni
Practice Exam Questions
Isotopes are
A. Atoms that have the same atomic number but
different numbers of electrons.
B. Atoms that have different numbers of protons
but have the same mass number.
C. Atoms that have both the same number of
protons and neutrons.
D. Atoms that have the same number of protons
but different mass numbers.
Practice Exam Questions
Which of the following is not an
empirical formula?
A. C2H6
B. CH3COOH
C. H2SO4
D. KCl
Practice Exam Questions
The number of atoms present in 0.625
mol of H2O molecules is:
A. 6.25 x 1021
B. 6.25 x 1022
C. 6.25 x 1023
D. 6.25 x 1024
Practice Exam Questions
The ground state electronic configuration,
in terms of subshells, for the chloride ion
is:
A. 1s22s22p63s23p6
B. 1s22s22p63s23p5
C. 1s22s22p63s23p63d1
D. 1s22s22p63s23p53d1
Practice Exam Questions
The electronegativity values of elements in the periodic
table have been found to follow certain trends. The
correct statement concerning electronegativity values
is that they:
A. Increase from left to right across the periodic table
and increase as you go down the table.
B. Increase from left to right across the periodic table
and decrease as you go down the table.
C. Decrease from left to right across the periodic table
and decrease as you go down the table.
D. Decrease from left to right across the periodic table
and increase as you go down the table.
Practice Exam Questions
The ground state electronic configuration,
in terms of shells, for the chloride ion is,
A. 2, 8, 8.
B. 2, 8, 7.
C. 2, 8, 6.
D. 2, 8, 7, 1.
Practice Exam Questions
Practice Exam Questions
Practice Exam Questions
Practice Exam Questions
Practice Exam Questions