Genetics is a term that refers to the study of genes and their roles in inheritance
Water is molecule formed by the covalent bonding of two atoms of hydrogen with one atom of oxygen. The chemical and physical properties of water are different from each of it's constituent elements Oxygen and Hydrogen. The properties of a drop of water will depend on the simplest unit of water, which is the water molecule 
. Therefore, the smallest unit of the water drop that retains all the physical and chemical properties exhibited by a sample of water is the molecule.
There seems to be a mistake. If u mistyped the 'h', then the reaction is single replacement.
Answer:
The elements become less reactive.
Explanation:
As we move from left to right across the periodic table the number of valance electrons in an atom increase. The atomic size tend to decrease in same period of periodic table because the electrons are added with in the same shell. When the electron are added, at the same time protons are also added in the nucleus. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction and reactivity increases because of greater electron affinity.
As we move down the group atomic radii increased with increase of atomic number. The addition of electron in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased. The electron affinity decreases because of shielding effect and thus atom become less reactive.
