Chemistry 11
Review Solutions March 2011
1. An atom is the smallest particle of any element that contains protons, neutrons, and electrons.
2. - All matter is composed of extremely small, indivisible particles called atoms
- All atoms of a given element are identical (same properties); the atoms of different elements are different
- Atoms are neither created nor destroyed in chemical reactions, only rearranged
- Compounds are formed when atoms of more than one element combine
- A given compound always has the same relative number and kind of atoms
3. Proton, +1 charge, relative mass of 1
Neutron, 0 charge, relative mass of 1
Electron, -1 charge, relative mass of 1/1840 (approximately 2000 electrons would have the mass of 1
proton/neutron)
4. The nucleus is made up of protons and neutrons
5. The atomic number tells the number of protons in an atom of that element. The mass number tells you the
relative mass – # of protons + # of neutrons
6. Isotopes are atoms of the same element that have a different number of neutrons but the same number of
protons. The number of neutrons is different, and the mass number is different.
7.The atomic mass of an element is the average of the total number protons and neutrons in that element. The
atomic masses for most elements are not whole numbers because they are average atomic masses.
Average atomic mass is a number calculated depending on the abundances found in the world.
8. 6 protons and 6 electrons
9. sodium
10. The three isotopes of hydrogen differ by the number of neutrons in the atoms. The isotopes exist in nature
with 0, 1, or 2 neutrons. The most abundant is an atom of hydrogen with 0 neutrons.
11. 63.62 amu
12. Thompson observed that the cathode rays were affected by the presence of a magnet, he discovered the
electron. Rutherford observed that alpha particles were deflected by the atoms in the gold foil, therefore part
of the atom was dense enough, and the nucleus was discovered
13. Rutherford discovered that there exists a nucleus in an atom, and it contains the majority of the mass of the
atom. Bohr’s postulated that electrons exist in orbits with fixed energy.
14. Different colours are given off because energy being released. Electrons of the atoms gain energy (get
excited) from the flame or electricity and move to an outer energy level. When they give off this energy and
return to their ground state the energy is given off in the form of light.
15. The quantum mechanical model describes an atom with orbitals – locations to where electrons are located
16.Afbau Principle – electrons fill sublevels of lower energy before higher energy levels
Hund’s Rule – electrons in the same sublevel do not pair up until they have to
Pauil Exclusion Principle – electrons in the same orbital must have opposite spin.
2
2
17.a. carbon 1s 2s 2 p
2
2
2
2
6
2
c. chlorine 1s 2s 2 p 3s 3 p
2
10
e. arsenic [ Ar ]4s 3d 4 p
18. Valence Electrons
a. 4
b. 3
19. (a) Ti
(b) Zn
2
1
2
2
b. boron 1s 2s 2 p
5
d. beryllium 1s 2 s
3
c. 7
(c) Se
d. 2
e. 5
20. An electron is in the excited state when it has jumped to an outer energy level. An electron is found in the
ground state when it has not gained any energy and is orbiting the nucleus in its original orbit.
21. When atoms are isoelectronic they contain the same number of electrons.
22. (a) The atomic radius decreases as you go left to right across a period and increases as you go down a
group. Across a period the inside electrons are less effective at blocking the nuclear charge as the number of
protons increases, and the atomic size decreases. When going down a group the number of inside energy
levels increases, and the size of the atoms increase as well.
(b) More energy is required to remove an electron from a smaller atom because the attractive force between
the nucleus and the outside electrons is stronger. Therefore, more IE is required to the right of a period and
near the top of a group.
23. (a) N (b) Au
(c) K
(d) Ga
Elements found in the same group have a larger atomic radius the farther down a group because there are
more energy levels.
Elements found in the same period have a larger atomic radius the farther left because the inside electrons
can block the smaller positive charge. The more of the positive charge that can reach the outside electrons
the stronger the attraction, making the atomic size smaller.
24. (a) O (b) Ag
(c) Ca
(d) Ge
The smaller atomic radius means there is a large attraction between the nucleus and the outside electrons.
The stronger the attraction the more ionization energy would be required to remove an electron.
25. (a) Ca, calcium
(b) Ne, neon
26. (a) representative metal
(c) transition metal
(e) representative metal
(c) K, potassium
(d) I, iodine
(e) Po, polonium
(b) transition metal
(d) nonmetal
(f) metalloid
27. What are the physical properties of metals?
Physical properties of metals include: good conductors of heat and electricity, luster, malleable, ductile, high
densities, high boiling points, high melting points, they resist stretching and twisting, and are solids at room
temperature.
What are the physical properties of nonmetals?
Physical properties of nonmetals include: no luster, poor conductors, low densities, low melting points, low
boiling points, and they may be solid, liquid, or gas at room temperature.
Metalloids have physical properties of both metals and nonmetals
28. Who is Dmitri Mendeleev, and what was his contribution to chemistry?
Dmitri Mendeleev was a Russian scientist credited with creating the first periodic table. He arranged all of
the known elements in order of increasing atomic mass. He placed the elements in rows and columns so
that elements with similar properties would be located together. He left blank spaces in his periodic table
where no known elements seemed to fit. He explained that these blank spaces represented elements that
had not yet been discovered, and based on their position in the periodic table, Mendeleev was able to
predict the properties of these undiscovered elements. When these elements were discovered, their
properties were very similar to those predicted by Mendeleev.
How is the modern periodic table different from the one created by Mendeleev?
The modern periodic table contains more elements than the one created by Mendeleev because more
elements have been discovered, this is not a significant difference however. The main difference between
Mendeleev's periodic table and the modern periodic table is that Mendeleev's was arranged in order of
increasing atomic mass and the modern periodic table is arranged in order of increasing atomic number.
This corrects the few inconsistencies found in Mendeleev's table.
30. An atom has high electronegativity when it has a strong desire to attract electrons to itself to complete its outer
shell. Ex. Fluorine has a very small radius and is only one electron away from completing its outer energy level so it
would have a very high electronegativity.
31. An smaller atom (or one with a complete valence shell) will have a higher ionization energy because the
nucleus has a stronger attraction for the outside electrons. The largest atom will have a lower IE because of a
weaker attraction.
a) 1s2 2s2 3p6 3s2 3p6 4s2 3d10 4p6 5s1 Rb
b) 1s2 2s2 3p6 3s2 3p6 4s2
Ca
c) 1s2 2s2 3p6 3s2 3p6 4s2 3d104p6
Kr
iii) 409 kJ/mol
ii) 595 kJ/mol
i) 1356 kJ/mol
32. When an atom gains an electron (becomes an anion) it will have more e- orbiting the outer shell. The size of
the anion will be larger than the atom that is has come from.
When an atom loses an electron (becomes a cation) it will have fewer e- orbiting the outer shell. The attraction from
the nucleus to the outer e- will be stronger and the cation will be smaller than the atom it has come from.
33. Noble gases have full p sublevels. With full p sublevels the atoms are very stable, this means they do not want
to gain or lose any e-.
34. In any ___, the number of electrons between the nucleus and the outer energy level is the same.
b. group
35. The halogens are considered a ____.
b. group