Question

1. give two examples of elements for each category.

\ta) noble gases\t\t\t\t\td) alkaline earth metals
\tb) halogens
\tc) alkali metals

1. give the name and symbol for the element found at each of the following locations on the periodic table:

\ta) group 1; period 4\t\t\t\td) group 2; period 6
\tb) group 13; period 3
\tc) group 16; period 3

1. where are the alkali metals, alkaline earth metals, halogens, transition metals, and the noble gases located in the periodic table?

1. describe the relationship between the group number and the electron configuration of the elements in a group.

1. what trend in atomic radius do you see as you go down a group/family on the periodic table? what causes this trend?

1. what trend in atomic radius do you see as you go across a period/row on the periodic table? what causes this trend?

1. circle the atom in each pair that has the largest atomic radius.

\ta) al b\tb) s o\tc) br cl\td) na al\te) o f\tf) mg ca

1. arrange the following elements in order of decreasing atomic size: sulfur, chlorine, aluminum and sodium. explain if your arrangement demonstrates a periodic trend or a group trend

1. indicate whether the following properties increase or decrease from left to right across the periodic table.

\ta) atomic radius\t\t\t\td) electron affinity
\tb) first ionization energy
\tc) electronegativity

1. choose which statement about the alkali metals lithium and cesium is correct.

\ta) as the atomic number increases, the electronegativity of the elements increases
\tb) as the atomic number increases, the first ionization energy of the elements decreases

Explanation:

Problem 3a (Noble Gases)

Noble gases are in group 18 of the periodic table. Examples include Helium (He) and Neon (Ne). Helium has a stable electron configuration with 2 electrons in its outer shell, and Neon has 8 electrons in its outer shell, both being inert.

Problem 3b (Halogens)

Halogens are in group 17. Examples are Fluorine (F) and Chlorine (Cl). They are highly reactive non - metals and need one electron to complete their octet.

Problem 3c (Alkali Metals)

Alkali metals are in group 1. Examples are Lithium (Li) and Sodium (Na). They have one valence electron and are highly reactive, readily losing that electron to form +1 ions.

Problem 3d (Alkaline Earth Metals)

Alkaline earth metals are in group 2. Examples are Magnesium (Mg) and Calcium (Ca). They have two valence electrons and form +2 ions.

Problem 4a (Group 1; Period 4)

Group 1 elements are alkali metals. In period 4, the element is Potassium (K). The period number tells us the number of electron shells, and group 1 tells us the number of valence electrons (1).

Problem 4b (Group 13; Period 3)

Group 13 elements have 3 valence electrons. In period 3, the element is Aluminum (Al). Period 3 means there are 3 electron shells, and group 13 means 3 valence electrons.

Problem 4c (Group 16; Period 3)

Group 16 elements have 6 valence electrons. In period 3, the element is Sulfur (S). Period 3 has 3 electron shells, and group 16 has 6 valence electrons.

Problem 4d (Group 2; Period 6)

Group 2 elements are alkaline earth metals. In period 6, the element is Barium (Ba). Period 6 has 6 electron shells, and group 2 has 2 valence electrons.

Problem 5

- Alkali metals: Group 1 (the first column on the left of the periodic table, excluding hydrogen).
- Alkaline earth metals: Group 2 (the second column).
- Halogens: Group 17 (the second - last column).
- Transition metals: Groups 3 - 12 (the middle - block of the periodic table).
- Noble gases: Group 18 (the last column).

Problem 6

For main - group elements (groups 1, 2, 13 - 18), the group number is equal to the number of valence electrons in the outermost shell of the element's atoms. For example, group 1 elements have 1 valence electron, group 2 has 2, group 13 has 3, and so on up to group 18 which has 8 (except helium with 2) valence electrons. This means that elements in the same group have similar chemical properties because they have the same number of valence electrons available for bonding.

Problem 7

Trend

As you go down a group (family) on the periodic table, the atomic radius increases.

Cause

When moving down a group, the number of electron shells (energy levels) increases. For example, in group 1, Lithium (Li) has 2 electron shells, Sodium (Na) has 3, Potassium (K) has 4, etc. Even though the nuclear charge also increases, the increase in the number of electron shells has a more significant effect on the atomic radius. The outermost electrons are further from the nucleus, and the shielding effect from inner electrons reduces the attractive force of the nucleus on the outermost electrons, leading to a larger atomic radius.

Problem 8

Trend

As you go across a period (row) from left to right on the periodic table, the atomic radius decreases.

Cause

Across a period, the number of protons in the nucleus (nuclear charge) increases while the number of electron shells remains the same. For example, in period 3, from Sodium (Na) to Chlorine (Cl), the number of protons increases from 11 to 17. The outermost electrons are in the same energy level, and the increasing nuclear charge pulls the electrons more tightly towards the nucleus, reducing the atomic radius.

Problem 9

a) Al and B

Al (Aluminum) is in period 3 and B (Boron) is in period 2. As we go down a group (both are in group 13), the atomic radius increases. So Al has a larger atomic radius.

b) S and O

S (Sulfur) is in period 3 and O (Oxygen) is in period 2. Going down group 16, the atomic radius increases. So S has a larger atomic radius.

c) Br and Cl

Br (Bromine) is in period 4 and Cl (Chlorine) is in period 3. Going down group 17, the atomic radius increases. So Br has a larger atomic radius.

d) Na and Al

Na (Sodium) and Al (Aluminum) are in period 3. As we go from left to right across a period, the atomic radius decreases. Na is to the left of Al, so Na has a larger atomic radius.

e) O and F

O (Oxygen) and F (Fluorine) are in period 2. As we go from left to right across a period, the atomic radius decreases. O is to the left of F, so O has a larger atomic radius.

f) Mg and Ca

Mg (Magnesium) is in period 3 and Ca (Calcium) is in period 4. Going down group 2, the atomic radius increases. So Ca has a larger atomic radius.

Problem 10

Order (decreasing atomic size)

Sodium (Na) > Aluminum (Al) > Sulfur (S) > Chlorine (Cl)

Explanation of Trend

These elements are all in period 3 of the periodic table. As we move from left to right across a period, the atomic radius decreases. This is a periodic trend because it occurs across a row (period) of the periodic table. The nuclear charge increases from Na (11 protons) to Cl (17 protons) while the number of electron shells remains the same (3 shells for all). The increasing nuclear charge pulls the electrons more tightly, reducing the atomic radius.

Problem 11

a) Atomic radius

From left to right across the periodic table, the atomic radius decreases. This is because the nuclear charge increases while the number of electron shells remains the same, pulling electrons closer to the nucleus.

b) First ionization energy

First ionization energy generally increases from left to right across the periodic table. As the atomic radius decreases, the outermost electrons are more tightly held by the nucleus, so more energy is required to remove the first electron.

c) Electronegativity

Electronegativity increases from left to right across the periodic table. Elements on the right - hand side of the periodic table (non - metals) have a greater tendency to attract electrons in a chemical bond compared to elements on the left (metals).

d) Electron affinity

Electron affinity generally increases from left to right across the periodic table (with some exceptions). Non - metals have a greater tendency to gain electrons, so they have more negative (or higher) electron affinity values as we move from left to right.

Problem 12

Analyzing Option a

As the atomic number increases in alkali metals (going down group 1), the electronegativity decreases. This is because the atomic radius increases, and the outermost electrons are further from the nucleus, so the ability to attract electrons (electronegativity) decreases. So option a is incorrect.

Analyzing Option b

As the atomic number increases in alkali metals (going down group 1), the first ionization energy decreases. This is because the atomic radius increases, and the outermost electron is further from the nucleus, so less energy is required to remove it. So option b is correct.

of Trend
These elements are all in period 3 of the periodic table. As we move from left to right across a period, the atomic radius decreases. This is a periodic trend because it occurs across a row (period) of the periodic table. The nuclear charge increases from Na (11 protons) to Cl (17 protons) while the number of electron shells remains the same (3 shells for all). The increasing nuclear charge pulls the electrons more tightly, reducing the atomic radius.

Problem 11

a) Atomic radius

From left to right across the periodic table, the atomic radius decreases. This is because the nuclear charge increases while the number of electron shells remains the same, pulling electrons closer to the nucleus.

b) First ionization energy

First ionization energy generally increases from left to right across the periodic table. As the atomic radius decreases, the outermost electrons are more tightly held by the nucleus, so more energy is required to remove the first electron.

c) Electronegativity

Electronegativity increases from left to right across the periodic table. Elements on the right - hand side of the periodic table (non - metals) have a greater tendency to attract electrons in a chemical bond compared to elements on the left (metals).

d) Electron affinity

Electron affinity generally increases from left to right across the periodic table (with some exceptions). Non - metals have a greater tendency to gain electrons, so they have more negative (or higher) electron affinity values as we move from left to right.

Problem 12

Analyzing Option a

As the atomic number increases in alkali metals (going down group 1), the electronegativity decreases. This is because the atomic radius increases, and the outermost electrons are further from the nucleus, so the ability to attract electrons (electronegativity) decreases. So option a is incorrect.

Analyzing Option b

As the atomic number increases in alkali metals (going down group 1), the first ionization energy decreases. This is because the atomic radius increases, and the outermost electron is further from the nucleus, so less energy is required to remove it. So option b is correct.

Answer:

Problem 3

a) Noble gases: Helium (He), Neon (Ne)
b) Halogens: Fluorine (F), Chlorine (Cl)
c) Alkali metals: Lithium (Li), Sodium (Na)
d) Alkaline earth metals: Magnesium (Mg), Calcium (Ca)

Problem 4

a) Group 1; Period 4: Potassium (K)
b) Group 13; Period 3: Aluminum (Al)
c) Group 16; Period 3: Sulfur (S)
d) Group 2; Period 6: Barium (Ba)

Problem 5

• Alkali metals: Group 1
• Alkaline earth metals: Group 2
• Halogens: Group 17
• Transition metals: Groups 3–12
• Noble gases: Group 18

Problem 6

For main - group elements, the group number equals the number of valence electrons. Elements in the same group have similar electron configurations (same number of valence electrons), leading to similar chemical properties.

Problem 7

Trend: Increases down a group.

Cause: Number of electron shells increases, shielding increases, outermost electrons are farther from the nucleus.

Problem 8

Trend: Decreases across a period (left - to - right).

Cause: Nuclear charge increases (more protons) while electron shells remain the same, pulling electrons closer to the nucleus.

Problem 9

a) Circle Al
b) Circle S
c) Circle Br
d) Circle Na
e) Circle O
f) Circle Ca

Problem 10

Order: Sodium (Na) > Aluminum (Al) > Sulfur (S) > Chlorine (Cl). This is a periodic trend (across period 3, atomic size decreases left - to - right due to increasing nuclear charge).

Problem 11

a) Atomic radius: Decreases
b) First ionization energy: Increases
c) Electronegativity: Increases
d) Electron affinity: Increases (general trend, with exceptions)

Problem 12

Correct option: b) as the atomic number increases, the first ionization energy of the elements decreases