Question

1. which one of the following dot structures is incorrectly drawn?

a. (dot structures)
b. (dot structures)
c. (dot structures)
d. (dot structures)
e. (dot structures)

1. rutherford’s gold foil experiment was crucial in the development of atomic theory because it:

a. demonstrated that the atom contained a dense, positively charged nucleus.
b. demonstrated that electrons were embedded within a positive matrix.
c. demonstrated the idea that atoms were indivisible and indestructible.
d. demonstrated that the atom contained neutrons.

1. what principle states that atoms tend to form compounds so that each atom can have eight electrons in its outermost energy level?

a. rule of eights
b. avagadro’s principle
c. configuration rule
d. octet rule

1. what is the best method for reading the water level in a graduated cylinder?

a. eyes above the water level
b. eyes at the water level
c. eyes below the water level
d. holding the graduated cylinder up in the air to the level of your eyes

1. which of the following statements is correct?

a. the na⁺¹ ion is bigger than the neutral na atom because a(an) electron shell(s) are added when sodium (na) loses an electron
b. the na⁺¹ ion is smaller than the neutral na atom because a(an) electron shell(s) are removed when sodium (na) loses an electron
c. the na⁺¹ ion is bigger than the neutral na atom because nuclear charge is added when sodium (na) loses an electron
d. the na⁺¹ ion is smaller than the neutral na atom because nuclear charge is added when sodium (na) loses an electron

1. the trend in ionization energy as you move across a period is due to

a. increased number of protons and no increase in number of inner electrons to shield nucleus
b. decreased number of protons and no increase in number of inner electrons to shield nucleus
c. increased number of protons and an increase in number of inner electrons to shield nucleus
d. ionization energy does not change across a period

Explanation:

1. Q27:

• Option a: This is the correct Lewis structure for water ($\ce{H2O}$), oxygen has 8 valence electrons, each hydrogen has 2.
• Option b: This is the correct triple-bonded $\ce{N2}$ structure, each nitrogen has a full octet.
• Option c: This structure for $\ce{H2C=C=CH2}$ (allene) is incorrect. The central carbon only has 6 valence electrons instead of a full octet.
• Option d: This is the correct $\ce{HS^-}$ Lewis structure, sulfur has a full octet and carries a -1 charge.
• Option e: This is the correct $\ce{H3O^+}$ hydronium ion structure, oxygen has a full octet with a +1 charge.

1. Q28: Rutherford's gold foil experiment showed that most alpha particles passed through the foil undeflected, while a small number bounced back, proving the atom has a tiny, dense positively charged nucleus.
2. Q29: The octet rule is the principle that atoms tend to gain, lose, or share electrons to achieve a full valence shell of 8 electrons (2 for hydrogen).
3. Q30: To correctly read the meniscus of water in a graduated cylinder, your eyes must be level with the bottom of the curved water surface to avoid parallax error.
4. Q31: When neutral sodium loses its single valence electron to form $\ce{Na+}$, it loses its entire outermost electron shell, making the ion smaller than the parent neutral atom.
5. Q32: As you move across a period, the number of protons in the nucleus increases, increasing nuclear charge, while the number of inner shielding electrons stays the same. This pulls valence electrons closer, increasing ionization energy.

Answer:

1. Q27: c. $\boldsymbol{\ce{H2C=C=CH2}}$ incorrect Lewis structure
2. Q28: a. Demonstrated that the atom contained a dense, positively charged nucleus.
3. Q29: d. Octet rule
4. Q30: b. Eyes at the water level
5. Q31: b. The $\ce{Na^{+1}}$ ion is smaller than the neutral Na atom because a(an) electron shell(s) are removed when sodium (Na) loses an electron
6. Q32: a. increased number of protons and no increase in number of inner electrons to shield nucleus