1. A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms.
The bond is caused by the electrostatic forceof attraction between opposite charges, either between electrons and nuclei, or as the
result of a dipole attraction. The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic
bonds and "weak bonds" such as dipole–dipole interactions, the London dispersion force and hydrogen bonding.
Since opposite charges attract via a simple electromagnetic force, the negatively charged electrons that are orbiting the nucleus and
the positively charged protons in the nucleus attract each other. An electron positioned between two nuclei will be attracted to both
of them, and the nuclei will be attracted toward electrons in this position. This attraction constitutes the chemical bond. Due to
the matter wave nature of electrons and their smaller mass, they must occupy a much larger amount of volume compared with the
nuclei, and this volume occupied by the electrons keeps the atomic nuclei relatively far apart, as compared with the size of the
nuclei themselves. This phenomenon limits the distance between nuclei and atoms in a bond.
In general, strong chemical bonding is associated with the sharing or transfer of electrons between the participating atoms. The
atoms in molecules, crystals, metals and diatomic gases— indeed most of the physical environment around us— are held together
by chemical bonds, which dictate the structure and the bulk properties of matter.
Bonds in chemical formulas[edit]
The fact that atoms and molecules are three-dimensional makes it difficult to use a single technique for indicating orbitals and
bonds. In molecular formulas the chemical bonds (binding orbitals) between atoms are indicated by various methods according to
the type of discussion. Sometimes, they are completely neglected. For example, in organic chemistry chemists are sometimes
concerned only with the functional groups of the molecule. Thus, the molecular formula of ethanol may be written in a paper
in conformational, three-dimensional, full two-dimensional (indicating every bond with no three-dimensional directions), compressed
two-dimensional (CH3–CH2–OH), separating the functional group from another part of the molecule (C2H5OH), or by its atomic
constituents (C2H6O), according to what is discussed. Sometimes, even the non-bonding valence shell electrons (with the two-
dimensional approximate directions) are marked, i.e. for elemental carbon .
'
C'
. Some chemists may also mark the respective orbitals,
i.e. the hypothetical ethene−4
anion (
/
C=C/
−4
) indicating the possibility of bond formation.
Invasive or introduced pest species have caused many native animals and plants to become extinct across the world.
People use a lot of different crops and domesticated animals for farming, and a lot more animals and plants (like mice, rats,
cockroaches and weeds) live and thrive around us even if we don't want them to!
The growth of the human population is the biggest threat to natural environments today.
The 'O' stands for 'overharvesting' and 'overhunting'
Many of the world's biggest and most impressive animals, such as whales, elephants, rhinos and tigers, are now all
rare because they were hunted heavily in the past.

2. Mother to Son
BY LANGSTON HUGHES
Well, son, I’ll tell you:
Life for me ain’t been no crystal stair.
It’s had tacks in it,
And splinters,
And boards torn up,
And places with no carpet on the floor—
Bare.
But all the time
I’se been a-climbin’ on,
And reachin’ landin’s,
And turnin’ corners,
And sometimes goin’ in the dark
Where there ain’t been no light.
So boy, don’t you turn back.
Don’t you set down on the steps
’Cause you finds it’s kinder hard.
Don’t you fall now—
For I’se still goin’, honey,
I’se still climbin’,
And life for me ain’t been no crystal stair.