Periodic Trends

What are periodic trends?

• Periodic trends are patterns in the periodic table that show the variation of certain properties of elements.

• Periodic trends are the daily changes in the stock market.

• Periodic trends are the seasonal changes in weather patterns.

• Periodic trends are the fluctuations in daily temperature.

Answer explanation

Periodic trends refer to the observable patterns in the periodic table, such as atomic radius, electronegativity, and ionization energy, which change predictably across periods and groups.

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Which of the following increases across a period from left to right?

• A) Atomic Radius

• B) Ionization Energy

• C) Metallic Character

• D) Nonmetallic Character

Answer explanation

Ionization energy increases across a period from left to right due to increasing nuclear charge, which attracts electrons more strongly, making them harder to remove. Thus, the correct answer is B) Ionization Energy.

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In the periodic table, which trend decreases down a group?

• A) Electronegativity

• B) Atomic Radius

• C) Electron Affinity

• D) Ionization Energy

Answer explanation

Electronegativity decreases down a group due to increased atomic size and shielding effect, making it harder for atoms to attract bonding electrons. Thus, the correct answer is A) Electronegativity.

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NGSS.HS-PS1-1

According to Coulomb's Law, what happens as the atomic number increases?

• The nuclear attraction for electrons decreases.

• The nuclear attraction for electrons increases.

• The number of protons decreases.

• The number of protons remains the same.

Answer explanation

As the atomic number increases, the number of protons in the nucleus increases, leading to a stronger nuclear attraction for electrons. This increased positive charge pulls electrons closer, enhancing their attraction.

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Fill in the blank: As the atomic number increases, the nuclear attraction for electrons ______.

• increases.

• decreases.

• remains the same.

• fluctuates.

Answer explanation

As the atomic number increases, the number of protons in the nucleus increases, enhancing the nuclear attraction for electrons. Therefore, the correct answer is that the nuclear attraction for electrons increases.

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What is the relationship between the number of protons and the strength of positive nuclear charge?

• As the number of protons increases, the strength of positive nuclear charge decreases.

• As the number of protons increases, the strength of positive nuclear charge increases.

• The number of protons does not affect the strength of positive nuclear charge.

Answer explanation

The strength of positive nuclear charge is directly related to the number of protons in the nucleus. As the number of protons increases, the positive charge also increases, leading to a stronger nuclear attraction to electrons.

What is the atomic radius?

• The distance between the nuclei of two different atoms

• One-half the distance between the nuclei of two identical atoms bonded together

• The distance from the nucleus to the outermost electron

• The distance between the nucleus and the electron cloud.

Answer explanation

The atomic radius is defined as one-half the distance between the nuclei of two identical atoms bonded together. This measurement reflects the size of the atom in a bonded state, making it the correct choice.

The atomic radius tends to increase as you move ______ a group.

• DOWN

• UP

• ACROSS

• DIAGONALLY

Answer explanation

The atomic radius increases as you move DOWN a group due to the addition of electron shells, which increases the distance between the nucleus and the outermost electrons, resulting in a larger atomic size.

The atomic radius tends to increase as you move ______ in a period.

• LEFT

• RIGHT

• UP

• DOWN

Answer explanation

The atomic radius increases as you move LEFT in a period due to the decrease in effective nuclear charge, which allows the outer electrons to be held less tightly, resulting in a larger atomic size.

What is reactivity a measure of?

Answer explanation

Reactivity is a measure of how readily a substance undergoes a chemical reaction. It indicates the tendency of a substance to react with other substances, which is crucial in understanding chemical behavior.

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