Which describes the sahara?

tropical jungle with a variety of plants and animals

high plains on which many african animals live

a desert that covers the northern third of africa

the terrain between desert and savanna

The correct answer is - a desert that covers the northern third of Africa.

Sahara is the biggest desert in the world. It occupies the northern third of the African continent, thus being the absolutely most dominant landscape feature in North Africa. It stretches from the Atlantic coast on the west, to the Red Sea coastline on the east, and from the plateaus of Central Africa, to near the coastline of the Mediterranean sea. It is a desert that has been a natural barrier for the movement and dispersal of people, animals and plants since its formation, with its vastness, lack of water, lack of food, sand storms, extreme heat.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.