Answer:
Groups 1, 2, 13-18
Explanation:
The periodic table is divided into two broad categories: Main Group Elements and Transition Metals. The Main Group Elements include the alkali metals, alkaline earth metals, halogens, noble gases, and any groups not mentioned (see the answer).
Valence electrons are the electrons in the outermost shell, or energy level, of an atom. For example, oxygen has six valence electrons, two in the 2s subshell and four in the 2p subshell. We can write the configuration of oxygen's valence electrons as 2s²2p⁴
Answer:
145 hours
Explanation:
Since one hour of riding a bicycle takes up 505 kcal of energy. It is also stated that one gram of body fat is equal to 7.70 kcal. Also, it is given that 1 pound of body fat is equal to 454 g.
Hence;
1 Ib= 454 g
21 Ib= 21 × 454/1 = 9534 g
But
1g of body fat = 7.70kcal
9534 g of body fat = 9534 × 7.70 kcal/1 = 73411.8 kcal
If 505 kcal is lost in 1 hour
73411.8 kcal is lost in 73411.8 kcal × 1hour/505k cal = 145 hours
Physical changes<span> are </span>changes<span> affecting the form of a chemical </span>substance<span>, but not its chemical composition. </span>Physical changes<span> are used to separate mixtures into their component compounds, but </span>can<span> not usually be used to separate compounds into chemical elements or simpler compounds.</span>