Iwill give 25 plz chemistry questions! which of the following formulas represents a molecular (i. e. covalent) compound? a. cacl2 b. h2o c. naoh d. lif according to the aufbau principle, a. electrons enter orbitals of lowest energy first. b. electrons enter orbitals of highest energy first. c. an orbital may be occupied by only two electrons. d. electrons in the same orbital must have opposite spins. 26.8 moles of argon contain how many atoms? a. 2.24 × 1022 atoms b. 1.61 × 1023 atoms c. 2.24 × 1024 atoms d. 1.61 × 1025 atoms group 17 (i. e. 7a) elements have electron(s) in their valence shell. a. 1 b. 6 c. 7 d. 8 in which of the following is the symbol for the ion and the number of electrons it contains given correctly? a. s+2; 18 electrons b. k+; 18 electrons c. i+; 54 electrons d. b+3; 8 electrons in metallic bonding, the electrons a. are unable to move. b. are shared between two single atoms. c. are given to one atom by another atom. d. are in a "sea" around the protons of all the metal atoms.

Answers:

1)Which of the following formulas represents a molecular (i.e. covalent) compound?

B. H₂O

Explanation: CaCl, NaOH and LiF are ionic compounds. In H₂O the bonds between atoms are covalent bonds.

2)According to the Aufbau principle,

A. electrons enter orbitals of lowest energy first.

Explanation: Aufbau principle explains how the electrons are located in the different orbitals, starting with the first level of lowest energy to the last level as follows:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f¹⁴6d¹⁰7p⁶

3)26.8 moles of argon contain how many atoms?

D. 1.61 × 1025 atoms

Explanation:

1 mol = 6.022 ₓ 10²³ atoms

atoms= 26.8 mol ₓ 6.022 ₓ 10²³ atoms/mol = 1.61 × 10²⁵ atoms

4)Group 17 (i.e. 7A) elements have electron(s) in their valence shell.

C. 7

Explanation: in Group 17 are the halogen elements, which have 7 electrons in their valence shell, with an electronic configuration 1s² 2p⁵ (two electrons in s orbital and 5 electrons in p orbital)

5)In which of the following is the symbol for the ion and the number of electrons it contains given correctly?

K+; 18 electrons

Explanation: the atomic number of potassium element (K) is 19, so its number of electrons is 19. To form the cation K⁺, it must loss 1 electron to have 1 positive charge. The remaining electrons after losing an electron is 18.

6) In metallic bonding, the electrons

D. are in a "sea" around the protons of all the metal atoms.

Explanation: metallic bonding exists in metals (such as Fe, Ni, Cu). The electrons are not located in one particular atom, but they can move from one atom to another by forming a mass or "sea" of electrons surrounding the protons. For this reason, metals can conduct electricity.