A zygote is the initial cell formed after a sperm and egg have joined. A blastocyst begins at day 5 in mammals after fertilization. This all occurs during the first week of being conceived. After the first week, the developing life form becomes an embryo, and the embryo is the stage where DNA is built..After week 9 in a human lifeform, it is considered a fetus. zygote is the initial cell formed after a sperm and egg have joined. A blastocyst begins at day 5 in mammals after fertilization. This all occurs during the first week of being conceived. After the first week, the developing life form becomes an embryo, and the embryo is the stage where DNA is built..
A covalent chemical bond results from the sharing of electrons between two atoms with similar electronegativities A single covalent bond represent the sharing of two valence electrons (usually from two different atoms). The Lewis structure below represents the covalent bond between two hydrogen atoms in a H2 molecule.
The Covalent Bond. Atoms can combine to achieve an octet of valence electrons by sharing electrons. Two fluorine atoms, for example, can form a stable F 2 molecule in which each atom has an octet of valence electrons by sharing a pair of electrons. A pair of oxygen atoms can form an O 2 molecule in which each atom has a total of eight valence electrons by sharing two pairs of electrons. The term covalent bond is used to describe the bonds in compounds that result from the sharing of one or more pairs of electrons.