Practice MCQ Questions and answers on Chemistry-GK

Two oxygen atoms can both achieve stable structures by sharing two pairs of electrons as in the diagram. Two electrons of each of the atom in the oxygen molecule make the double bond with each other. The double bond is shown conventionally by two lines joining the atoms. Each line represents one pair of shared electrons.

There are 1 one electron in a hydrogen atom.

The third shell of an atom can have a maximum of 18 electrons.

Bohr and Rutherford developed the model of atomic structure.

Ionic compounds are made up of a metal and nonmetal, and covalent compounds are made up of two nonmetals. In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds.

Atomic number of a chemical element is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus. It determines the place of an element in the periodic table. In an uncharged atom, the atomic number is also equal to the number of electrons.

The chemical behavior of atoms is determined by the number and the configuration of the electrons in the atom.

The general electronic configuration of group 15 elements (N, P, As, Sb and Bi) is ns²np³. Since Nitrogen has smallest size and greatest electronegativity in the family, it may gain three electrons and attain noble gas configuration, forming nitride N^3- ions. The other members show little tendency to form tri-negative M^3- ions. Their electronegativity is so low that they would generally form covalent compounds even with highly electropositive elements.

Mammalian erythrocytes are unique among the vertebrates as they are non-nucleated cells in their mature form. These cells have nuclei during early phases of erythropoiesis, but extrude them during development as they mature in order to provide more space for hemoglobin. In mammals, erythrocytes also lose all other cellular organelles such as their mitochondria, Golgi apparatus and endoplasmic reticulum.

Iron metal is more reactive than copper. Therefore, it can displace copper from copper sulphate (CuSO₄) solution. Cu is less reactive than iron, therefore, cannot replace iron from iron sulphate (FeSO₄).