Question

purpose: to determine the trends of the periodic table relating to atomic radius, first ionization energy, and electronegativity, and practice methods of graphing.
materials:

• chemistry reference table (table s)
• graph paper(s) – 3
• blank periodic table(s) - 3
• pen/pencil

methods:

1. look at your chemistry reference table (table s) and locate atomic radius column. using graph paper and blue colored pencil, plot the atomic number (1-20) on the x - axis and the atomic radius on the y - axis.
2. observe the trend as you go down the group and as you go across the period. record this trend in the data section. in other words, for data analysis 1, fill in the values for each property (using the same color scheme and order).
3. repeat steps 2 - 5 for first ionization energy (in green) and electronegativity (in red).

data analysis 1
periodic table - like structure with h, li, na, k, rb, cs on the left; mg, al, si, p, s, cl, ar on the right. arrows for across period (→) and down group (↓). questions:
across a period (→) atomic radius tends to ________.
across a period (→) first ionization energy tends to ________.
across a period (→) electronegativity tends to ________.
down a group (↓) atomic radius tends to ________.
down a group (↓) first ionization energy tends to ________.
down a group (↓) electronegativity tends to ________.
data analysis 2 (answer on looseleaf!)
atomic radius

• this trend ________ in a group from top to bottom. explain the reason for this tendency.
• this trend ________ across a period from left to right. explain the reason for this tendency.

first ionization energy

• this trend ________ in a group from top to bottom. explain the reason for this tendency
• this trend ________ across a period from left to right. explain the reason for this tendency.

electronegativity

• this trend ________ in a group from top to bottom. explain the reason for this tendency
• this trend ________ across a period from left to right. explain the reason for this tendency.

Answer:

Data Analysis 1 (Trends Across a Period and Down a Group)

Across a Period (→)

• Atomic Radius: As you move from left to right across a period, the atomic radius tends to decrease. This is because the number of protons in the nucleus increases, leading to a stronger positive charge that pulls the electrons closer to the nucleus. The number of electron shells remains the same, so the effective nuclear charge increases, reducing the atomic size.
• First Ionization Energy: Across a period, first ionization energy tends to increase. The increasing nuclear charge makes it harder to remove an electron from the outermost shell. Electrons are held more tightly, so more energy is required to ionize the atom.
• Electronegativity: Electronegativity tends to increase across a period. The increasing nuclear charge and decreasing atomic radius make atoms more likely to attract electrons in a chemical bond.

Down a Group (↓)

• Atomic Radius: Down a group, atomic radius tends to increase. Each element has an additional electron shell compared to the one above it. The outermost electrons are farther from the nucleus, so the atomic size expands.
• First Ionization Energy: First ionization energy tends to decrease down a group. The outermost electrons are farther from the nucleus and experience more shielding from inner electron shells. This makes it easier to remove an electron, requiring less energy.
• Electronegativity: Electronegativity tends to decrease down a group. The increasing atomic radius and shielding effect reduce the nucleus’s ability to attract electrons in a bond.

Data Analysis 2 (Explanations)

Atomic Radius

• In a group (top to bottom): The trend is increasing. Reason: Each element down a group has an additional electron shell. The outermost electrons are in a shell farther from the nucleus, so the atomic size increases.
• Across a period (left to right): The trend is decreasing. Reason: The number of protons (nuclear charge) increases, but the number of electron shells remains the same. The stronger nuclear charge pulls electrons closer, reducing the atomic radius.

First Ionization Energy

• In a group (top to bottom): The trend is decreasing. Reason: Electrons in lower groups are in shells farther from the nucleus and have more shielding from inner electrons. This makes it easier to remove an electron, so less energy is required.
• Across a period (left to right): The trend is increasing. Reason: The nuclear charge increases, so electrons in the outermost shell are held more tightly. More energy is needed to overcome this attraction and remove an electron.

Electronegativity

• In a group (top to bottom): The trend is decreasing. Reason: Larger atomic radius and increased shielding reduce the nucleus’s ability to attract bonding electrons.
• Across a period (left to right): The trend is increasing. Reason: Smaller atomic radius and higher nuclear charge make atoms more effective at attracting electrons in a chemical bond.

Final Answers (Filling in the Blanks)

Data Analysis 1

• Across a period (→):

Atomic radius: decrease
First ionization energy: increase
Electronegativity: increase

• Down a group (↓):

Atomic radius: increase
First ionization energy: decrease
Electronegativity: decrease

Data Analysis 2

• Atomic Radius:
• In a group: increases (reason: additional electron shells).
• Across a period: decreases (reason: increasing nuclear charge, same electron shells).

• First Ionization Energy:
• In a group: decreases (reason: increased shielding, larger radius).
• Across a period: increases (reason: increased nuclear charge, tighter electron hold).

• Electronegativity:
• In a group: decreases (reason: larger radius, reduced electron attraction).
• Across a period: increases (reason: smaller radius, higher nuclear charge).