Question

name: dexon williams date: sep.5,2025 period: 1 physical science unit 2 quiz circle the correct answer and answer in complete sentence. 1. what does the atomic number of an element represent? a. number of neutrons b. number of electrons c. number of protons d. atomic mass 2. what trend is observed in atomic radius across a period? a. increases b. decreases c. remains constant d. varies randomly 3. what are valence electrons? a. electrons in the nucleus b. electrons in the outer shell c. electrons in the inner shell d. protons in the outer shell 4. how is the periodic table arranged? 5. why are noble gases considered stable? 6. what is electronegativity and how does it change across the periodic table? 7. what is the octet rule? a. atoms want 8 neutrons b. atoms want 8 electrons in outer shell

Explanation:

1. The atomic number is defined as the number of protons in an atom's nucleus.
2. Across a period, the effective nuclear charge increases, pulling electrons closer, so atomic radius decreases.
3. Valence electrons are the electrons in the out - ermost shell of an atom and are involved in chemical bonding.
4. The periodic table is arranged in order of increasing atomic number, with elements in the same group having similar chemical properties due to the same number of valence electrons.
5. Noble gases are stable because they have a full outer electron shell, usually 8 electrons (octet), which gives them a low reactivity.
6. Electronegativity is the ability of an atom to attract electrons in a chemical bond. It increases across a period from left to right due to increasing nuclear charge and decreasing atomic radius.
7. The octet rule states that atoms tend to gain, lose, or share electrons to have 8 electrons in their outer shell for stability.

Answer:

1. C. Number of protons
2. B. Decreases
3. B. Electrons in the outer shell
4. The periodic table is arranged in order of increasing atomic number, with elements grouped by similar chemical properties.
5. Noble gases are considered stable because they have a full outer electron shell.
6. Electronegativity is the ability of an atom to attract electrons in a chemical bond. It increases across a period.
7. B. Atoms want 8 electrons in outer shell