The people use Earth's motion to determine units of time because of its uniform motion which is consistent.
<u>Explanation:</u>
In earlier days, people used to observe the motion of Earth to measure time. This is because, the Earth is moving at constant speed and at constant acceleration. So the change in position of the sun or stars can be easily correlated to the time.
Due to the consistency in the Earth's motion and the accurate repetition of the time period along with the seasons, the Earth's motion can be considered as a responsible source to determine the units of time.
Answer:
C. Lose three electrons to have a full outer shell
Explanation:
Al is in Group 13 of the Periodic Table, so it has three valence electrons.
It must either lose three electrons or gain five to achieve a stable octet.
It is easier to lose three electrons than it is to gain five, so Al loses three electrons.
D. is wrong, for the same reason.
A. is wrong. If Al lost three electrons, it would be breaking into a stable inner shell.
C. is wrong. Al is a metal, so it will lose electrons in a reaction.
Explanation:
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There are 3 significant digits in 5.40.
(To help understand): Sig figs are just a way of simplifying a number.