1. Which of the following groupings contains only representative elements?

1. Which of the following groupings contains only representative elements?

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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.

Also Read :   What leads to the formation of an ionic bond with Hg2+?

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