What is pH-scale? How to understand?
pH-scale starts from zero to 14 (0-14). pH 0-6 is considered as Acidic while 8-14 is considered basic and 7 is neutral. Taking 7 as a central point as you go away from 7 either acidity or basicity will increase. The 7-to-0 acidity will increase, a solution with pH 3 will be strongly acidic than a solution with pH 5. similarly basicity increase from 7-to-14.
In the periodic table, Why atomic size increases from top to bottom?
The periodic table is divided into periods (horizontal rows) and groups (vertical columns). The period number represents the number of shells (of that element in that period). Example: consider the 1st group-----going from to bottom period number will increase. The 1st element will be hydrogen (1st period), second will be Lithium (2nd period), 3rd Sodium (3rd period) then so on. These elements are in the same group but in different periods. Elements of 1st period have = one shell Elements of 2nd period have = two shells & so on Answer:: Because the number of shells from top to bottom increases so the size of the atom will increase from top to bottom.
What is DNA and why is it called double helix molecule?
DNA stands for deoxyribonucleic acid, which is a double-stranded and double helix molecule. The term helix refers to the structure of DNA. Two strands of DNA, which are backbones of DNA, are coiled with each-other in such a way that they form two grooves (1) Major groves (2) Minor grooves. Because these grooves (curves) are asymmetric, that is why DNA is a double helix. Actually, this shape of DNA is determined by bond angles in the sugar-phosphate backbone.