Answer: D. Sends small electrical impulses to the heart, causing it to beat more
Explanation: A pacemaker is implanted in the chest and helps to treat abnormal heart rhythms especially those causing your heart to skip beats or beat too slow.
Answer: They are referred to as isotopes, which are a form of an element that has different numbers of neutrons in their nucleus.
If one or more of the following occur: Gas formation, precipitate formation, color change, temperature change, or odor
Answer: The correct option is 3.
Explanation: We are given a compound which is made up of iron and oxygen only. The ratio of the two are given as:
This means that, number of iron ions are 2
Number of oxide ions are 3
From the above information, the formula becomes : 
The valency of iron = 3
Valency of oxide = 2
This compound is named as iron (III) oxide.
Hence, the correct option is 3
Answer:
Between carbon and silicon, silicon element has the strongest attraction between its nucleus and its valence electrons.
because silicon's nucleus is bigger than carbon.silicon loses electrons easily than carbon.
