Answer:
Explanation:
atomic mass
In 1869, Mendeleev published the first periodic table of the elements. In his periodic table, Mendeleev arranged elements in rows by increasing atomic mass. Within a row, elements with lower atomic masses were on the left. Mendeleev started a new row every time the chemical properties of the elements repeated.
Answer:
The correct answer is 5s
Explanation:
Strontium atomic number = 38
Electronic configuration is 
As 
orbital is valence orbital in strontium, the outer electrons exists in that orbital only.
Answer:
The correct option is d
Explanation:
Nuclide is synonymous with groups of electrons or protons, that is, a nuclide is the grouping of nucleons.
Answer: Most of the stars in the universe are main sequence stars — those converting hydrogen into helium via nuclear fusion. A main sequence star may have a mass between a third to eight times that of the sun and eventually burn through the hydrogen in its core. Over its life, the outward pressure of fusion has balanced against the inward pressure of gravity. Once the fusion stops, gravity takes the lead and compresses the star smaller and tighter.
Temperatures increase with the contraction, eventually reaching levels where helium is able to fuse into carbon. Depending on the mass of the star, the helium burning might be gradual or might begin with an explosive flash.
<span>An acid is a compound that produces hydrogen ions when dissolved in water. The pH of acid is less than 7 because it is rich in H+ concentration. Basic solutions have pH greater than 7 because it is rich in OH-. Neutral solutions meanwhile have pH equal to 7.</span>
