Determine whether each observation describes a chemical or a physical property 1. When a piece of Sodium metal is placed in a test tube with water, the Sodium fizzes and
bubbles of gas are produced.
2. When salt is added to water in a test tube, the salt dissolves.
3. When water is placed in a freezer at zero degree selcious it becomes ice.
4. When an iron bicycle is left outdoors and is exposed to moist air, it gets rusty.

chemical, physical, physical, chemical

Explanation:

both rust and bubbles are products of chemical change whilst freezing ad dissolving are physical.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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~ trueboss72

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8