Nursing Elites

1. How many electron pairs are shared to form a double covalent bond?

• A. 1
• B. 2
• C. 3
• D. 4

Correct answer: B

Rationale: The correct answer is B. In a double covalent bond, two pairs of electrons are shared between two atoms. This sharing of two electron pairs results in a stronger bond compared to a single covalent bond where only one pair of electrons is shared. Choice A is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choices C and D are incorrect as they do not represent the correct number of electron pairs shared in a double covalent bond.

2. What number represents the number of protons an element has?

• A. Atomic mass
• B. Mass number
• C. Atomic number
• D. Neutron number

Correct answer: C

Rationale: The correct answer is C, atomic number. The atomic number corresponds to the number of protons in an element. This number is unique to each element and determines its placement on the periodic table. It is equal to the number of protons found in the nucleus of an atom of that element. Choice A, atomic mass, represents the average mass of an element's isotopes. Choice B, mass number, is the sum of protons and neutrons in an atom. Choice D, neutron number, specifically refers to the count of neutrons in an atom and not protons.

3. On what concept is Kelvin based?

• A. Freezing point
• B. Absolute zero
• C. Boiling point
• D. Evaporation point

Correct answer: B

Rationale: The correct answer is B: Absolute zero. Kelvin is based on the concept of absolute zero, which is the point where molecular movement ceases entirely. This temperature scale starts at absolute zero (0K), where theoretically no molecular movement occurs. Choices A, C, and D are incorrect because Kelvin is not based on the freezing point, boiling point, or evaporation point, but rather on the absolute absence of molecular motion.

4. What is the correct formula for sodium nitrate?

• A. NaNO
• B. Na NO
• C. NaNO₃
• D. Na NO₂

Correct answer: C

Rationale: The correct formula for sodium nitrate is NaNO₃. In this formula, 'Na' represents sodium, 'N' represents nitrogen, and 'O₃' represents three oxygen atoms. Sodium nitrate consists of one sodium ion (Na⁺) and one nitrate ion (NO₃⁻), which means the correct formula is NaNO₃. Choice A (NaNO) is incorrect as it lacks the subscript indicating the presence of three oxygen atoms. Choice B (Na NO) is incorrect as it includes a space between 'Na' and 'NO', which is not part of the standard chemical formula notation. Choice D (Na NO₂) is incorrect as it indicates a different compound with a nitrite ion (NO₂⁻) instead of nitrate ion.

5. Which is a triatomic allotrope of oxygen?

• A. Ozone
• B. Water
• C. Acidic oxide
• D. Carbon dioxide

Correct answer: A

Rationale: Ozone (O3) is a triatomic allotrope of oxygen. It differs from the common diatomic oxygen molecule (O2) by having three oxygen atoms bonded together. Ozone is known for its protective role in the Earth's atmosphere, absorbing most of the Sun's harmful ultraviolet radiation. Water (H2O) is a compound composed of two hydrogen atoms and one oxygen atom. Acidic oxide and carbon dioxide are not triatomic allotropes of oxygen. Carbon dioxide consists of one carbon atom and two oxygen atoms, while acidic oxides refer to compounds where oxygen is bonded with other elements to form oxides, and they are not allotropes of oxygen.

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