Study guide for periodic table trends.
1.
A. By referring to electron arrangements and using information from Table 8 of the Data booklet, explain the
difference in radius for each of the following pairs:
(i)
Na and Na+ Na=2,8,1 > Na+= 2,8 Na+ because only 2 energy levels and the outer level is full so greater
nuclear charge
(ii)
Na+ and F- Na+= 11P and 10e so great nuclear charge so smaller radius< F- 9p and 10e so less charge
attractions same number of electrons.
B. By referring to atomic structure and using information from table 6 of the data booklet, explain the difference in
melting point for each of the following pairs:
(i) Na and Mg Mg> na more protons so greater attractions Mg 2+ more delocalized electrons than Na+ so has
greater nuclear charge
(ii) F2 and Cl2 Cl>F because more electrons and greater intermolecular van der waal’s forces
2.
(a) State and explain the term electronegativity. The ability of an atom to attract a bonding pair of electrons.
(b). state and explain the trend in electronegativity across period 3 from Na to Cl. Electronegativity increases from
Na to Cl because the number of protons increases so nuclear charge increases so that the electrons are pulled
closer to the nucleus and size of atoms decrease
(c ) explain why Cl2 rather than Br2 would react more vigorously with the solution of I-
Cl2 is a stronger oxidizing agent because it is on a lower energy level so that its valence electrons are closer to the nucleus
so that is an increase in nuclear charge. It has a greater attraction for electrons so has a higher electron affinity.
3. Define the following terms
(i)
Atomic number: number of protons in the nucleus
(ii)
Mass number: number of protons and neutrons in the nucleus
4. Explain the following statements.
The first ionization energy of sodium is
(i)
Less than that of magnesium.
(ii)
Greater than that of potassium
b. The electronegativity of chlorine is higher than that of sulfur.
5. (a) nitrogen is found in period 2 and group 5 of the periodic table.
(i) distinguish between the terms period and group : period is a horizontal row and all elements on this horizontal
row have the same number of energy levels, where group is the vertical column and all these elements have the
same number of valence electrons.
(ii) state the electron arrangement of nitrogen and explain why it is found in period 2 and group 5 of the periodic
table 2,5 electrons are found in 2 energy levels which is meaning fro period two and have 5 valence electrons
which is why in group 5
(b) Table 8 of the data booklet gives the atomic and ionic radii of elements. State and explain the difference
between
(i) the atomic radius of nitrogen and oxygen atomic radius of nitrogen > oxygen because oxygen has a greater
nuclear charge so has greater attraction for the outer electrons
(ii) tha atomic radius of nitrogen and phosphorus: atomic radius of P> N because P has outer electrrons in an
energy level further from the nucleus so more nuclear shielding
(iii)
The atomic and ionic radius of nitrogen
6. Explain the following statements:
A. The first ionization energy of sodium is
(I)
Less that magnesium: Na has lower nuclear charge because of the number of protons so will have a larger
atomic radius because electrons are further from nucleus
(II)
Greater than potassium: Na is on a fewer energy levels and so electrons are closer to the nucleus on a
lower energy level than K which has a greater shielding effect because on higher energy level and more
electrons.
B. the electronegativity of chlorine is higher than that of sulfur. Chlorine is more electronegative than sulfur
because it has a higher nuclear charge, it attracts the electron pair.
7.
Table 6 of the Data booklet lists melting points of the elements. Explain the trend in the melting points of the
alkali metals, halogens and period 3 elements.
Alkali metals: metallic bonding is a bed of cations in a sea of electrons and as radius increases down the group ,
valence electrons are further away from nucleus due to nuclear shielding so strength of metallic bonding
decreases
Halogens: non-polar so held together by van der waal’s forces between molecules as size increases van der
waals forces increases and so will melting point.
Period 3 elements: increase in melting points of na , Mg and Al due to increase in number of valence electrons
and a decrease in size due to nuclear charge
Silicon: network covalent solid with very high melting point
Phosphorus to Argon simple molecular substances with weak van der waal’s forces and lower melting points
because of decreasing mass or size
(b) (i) explain how the first ionization energy of k compares with that of Na and Ar. K is less than Na because
electron removed from K is from higher energy level so further from nucleus so will have less nuclear charge
and greater nuclear shielding .
K is less than Ar because is from higher energy level the electrons are further from the nucleus so greater
shielding effect and smaller nuclear charge
(iii)
explain the difference between the first ionization energies of Na and Mg.
Mg has greater nuclear charge because has one more proton on same energy level so greater pull and
smaller atomic radius so more strongly attract to nucleus
(iv)
Suggest why more energy is needed to remove an electron from Na+ than from Mg+.
Na +1 is more stable because outer energy level is full so much pull from lower energy level, n=2 whereas
taking one electron from Mg leaves behind one more electron in n=3.
8. Explain why
(i)
The first ionization energy of magnesium is lower than that of fluorine? Electron removed from higher
energy level so valence electrons are further from the nucleus which means a greater atomic radius so
there is an increase shielding effect
(ii)
Magnesium has a higher melting point than sodium? Mg has twice as many delocalized electrons in
outer energy level (2 not 1) so the ionic charge is twice as big Mg2+ to Na+ so electrostatic attraction
between ions and electrons is greater.
9. Which is related to the number of electrons in the outer main level of the elements form the alkali metals to
the halogens?
I.
10.
a.
b.
c.
d.
11.
I.
a.
b.
c.
d.
GROUP NUMBER II. PERIOD NUMBER
A. I only
B. II only
C. Both I and II
D. Neither I nor II.
Which pair of elements reacts more readily?
Li + Br2
Li + Cl2
K + Br2
K +Cl2
Which of the following properties of the halogens increase from F to I?
ATOMIC RADUIS
II. MELTING POINT
III. ELECTRONEGATIVITY
A. I ONLY
B. I AND II ONLY
C. I AND III ONLY
D. I, II AND III
12. Element X is in group 2 and element Y is in group 7, of the periodic table. Which ions will be present in the
compound formed when X and Y react together?
a. X+ and Yb. X2+ and Y –
c. X + and Y 2d. X2- and Y +
13. For which element are the group number and the period number the same?
a. Li
b. Be
c. B
d. Mg
14. Which of the physical properties below decrease with increasing atomic number for both the alkali metals and
the halogens?
I.
ATOMIC RADIUS
II. IONIZATION ENERGY
II.
MELTING POINT
I only
II only
III only
I and III only
15. Rubidium is an element in the same group of the periodic table as lithium and sodium. It is likely to be a metal
which has a
a. High melting point and reacts slowly with water.
b. High melting point and reacts vigorously with water.
c. Low melting point and reacts vigorously with water.
d. Low melting point and reacts slowly with water.
16. When the following species are arranged in order of increasing radius, what is the correct order?
a. Cl-, Ar, K+
b. K+, Ar, Clc. Cl-, K+, Ar
d. Ar, Cl- K+
17.
a.
b.
c.
d.
18.
a.
b.
c.
d.
19.
I.
II.
a.
b.
c.
d.
a.
b.
c.
d.
What increases in equal steps of one from left to right in the periodic table for the elements lithium to neon?
The number of occupied electron energy levels
The number of neutrons in the most common isotope
The number of electrons in the atom
The atomic mass
Which two elements react most vigorously with each other
Chlorine and lithium
Chlorine and potassium
Iodine and lithium
Iodine and potassium
Which factors lead to an element having a low value of first ionization energy?
Large atomic radius
III high nuclear charge
High number of occupied energy levels
a. I and II only
b. I and III only
c. II and III only
d. I , II and III
20. Which statement about electronegativity is correct?
a. Electronegativity decreases across the period
b. Electronegativity increases down the group
c. Metals generally have lower electronegativity values than nonmetals.
d. Noble gases have the highest electronegativity values.
21. Which statement is correct for a periodic table?
a. Ionization energy increases from Li to Cs.
b. Melting point increases from Li to Cs.
c. Ionization energy increases from F to I
d. Melting point increases from F to I.
22. Which of the following statements are correct?
I.
The melting points decrease from LiCs for the alkali metals
II.
The melting points increase from FI for the halogens
III.
The melting points decrease from NaAr for the period 3 elements
I and II only
I and III only
II and III only
I, II and III
23. Which properties decrease in value when descending group I?
I.
Atomic radius
II.
Ionization energy
III.
Electronegativity
I and II only
I and III only
II and III only
I, II and III
24. The ionization energies of three consecutive elements in the periodic table are 1680, 2080 and 494 k? mol-1
respectively. Which of the following shows the elements with these values?
a. O F
Ne
b. F Ne
Na
c. Ne Na
Mg
d. Na Mg
Al
25. Analytical chemists can detect amounts of amino acids as small as 2.0 x 10 -21 mol of a substance. How many
molecules does this represent?
a. 2.0 x 10 -21
b. 1.2 x 103
c. 6.0 x 1023
d. 3.0 x 10 44
26. In what order are the elements listed in the periodic table?
a. In order of relative atomic mass
b. In order of reactivity
c. In order of nuclear charge
d. In order of electronegativity
The graph shows the trend in a physical property down group 7 in the periodic table
F
27.
a.
b.
c.
d.
28.
a.
b.
c.
d.
29.
a.
b.
c.
d.
30.
a.
b.
c.
d.
31.
a.
b.
c.
d.
32.
Cl
Br
I
What is the physical property?
Atomic radius
Electronegativity
Density
Melting point
Which is the best definition of electronegativity?
Electronegativity is the energy required for a gaseous atom to gain an electron.
Electronegativity is the attraction of an atom for a bonding pair of electrons.
Electronegativity is the attraction between the nucleus and the valence electrons of an atom.
Electronegativity is the ability of an atom to attract electrons from another atom.
Which sample has the greatest mass?
6.0 x 1025 molecules of hydrogen
5.0 mol of neon atoms
1.2 x 1024 atoms of silver
1.7 x 102 grams of iron
Which is the correct definition of the mass number of an atom?
The total mass of neutrons and protons in the nucleus of the atom
The total mass of neutrons, protons, and electrons in the atom
The number of protons in the nucleus of the atom
The total number of neutrons and protons in the nucleus of the atom.
Which statement describes the trends of electronegativity values in the periodic table?
Values increase from left to right across a period and increase down a group.
Values increase from left to right across a period and decrease down a group.
Values decrease from left to right across a period and increase down a group.
Values decrease from left to right across a period and decrease down a group.
Which statement is correct for all elements in the same period?
a.
b.
c.
d.
33.
(I)
(II)
(III)
(IV)
(V)
They have the same number of electrons in the highest occupied energy level.
They have the same chemical reactivity.
They have the same number of occupied energy levels.
They have the same number of neutrons.
The graph o f the first ionization energy plotted against atomic number for the first twenty elements show
periodicity
Define the term first ionization energy and state what is meant by the term periodicity? The minimum energy
to remove one electron from a gaseous atom. Or the energy required to remove one mole of electrons from
one mole of gaseous atoms and periodicity is the repeating pattern of physical and chemical properties
State the electron arrangement of argon and explain why the noble gases, helium, neon and argon show the
highest first ionization energies for their respective periods. 2,8,8 and the outer energy level is full and the
increased nuclear charge so has greatest attraction for electrons.
A graph of atomic radius plotted against atomic number shows that the atomic radius decreases across the
period. Explain why chlorine has a smaller atomic radius than sodium. 17 protons in chlorine is greater than 11
protons in Na so Cl has a greater nuclear charge which will attract more outer electrons.
Explain why a sulfide ion, S2- is larger than a chloride ion, Cl-.S2- has 16 protons and 18 electrons where Cl- has
17 protons and 18 electrons so S will be larger cause has 1 less proton and will have less nuclear charge than Cl
so outer level electrons not held as strongly as Cl
Explain why the melting point of the Group 1 metals(LiCs) decrease down a group whereas the melting
points of the group 7 elements(fI) increase down the group. The radii of the metal atoms increase from Li to
Cs so the forces of attraction are less between them.
The forces of attraction between halogen molecules are van der waals forces increase with increasing mass and
number of electrons.