Question

PLEASE HELP !

1. Two atoms are the same element if they have the same _________.
A. Atomic number B. Number of neutrons C. Charge D. Number of Electron shells

2. Which statement about compounds is TRUE?


A. Compounds are chemical substances
B. Compounds form between two or more elements
C. both A and B
D. None of the above

3. Which of the following is correct regarding the chemical bond between hydrogen and
oxygen atoms in a water molecule?


A. results in an unusually strong bond
B. results in a nonpolar molecule of water
C. forms by a shared pair of electrons between hydrogen and oxygen
D. forms between the neutral poles of hydrogen and oxygen

4. Magnesium (a metal) and oxygen (a nonmetal) combine to form magnesium oxide
(MgO). The atoms are held together by strong electrostatic attractions between the
positive and negative charges of the atoms. Which type of bond holds these atoms
together?


A. Polar covalent
B. Ionic
C. Hydrogen
D. Covalent

Answer 1

Answer:1. C Protons/ charge

2.C both a and b

3.C

4. B

Explanation:

Answer 2

Answer:

For 1: The correct answer is Option A.

For 2: The correct answer is Option C.

For 3: The correct answer is Option C.

For 4: The correct answer is Option B.

Explanation:

• For 1:

Atomic number is defined as the number of protons or number of electrons that are present in a neutral atom. It is represented as 'Z'.

Element is defined as the substance which have same type of atoms. All the atoms of an element have same atomic number.

For Example: The atoms of sodium element will have atomic number 11.

Hence, the correct answer is Option A.

• For 2:

Compounds are defined as the substances which are formed by the chemical combination  of two or more than two types of atoms in a fixed ratio by their mass. For Example:  $H_2O,CO_2$ etc..

They are chemical substances because chemical property of elements forming a bond gets changed.

Hence, the correct answer is Option C.

• For 3:

Covalent bond is defined as the bond which is formed by the sharing of electrons between two atoms forming a compound. These bonds are formed between two non-metals.

Hydrogen is 1st element of the periodic table having electronic configuration of $1s^1$

This element require 1 electron to attain stability.

Oxygen is 8th element of the periodic table having electronic configuration of $1s^22s^22p^4$

This element require 2 electron to attain stability.

To form water molecule, 2 hydrogen atoms are required for every 1 atom of oxygen. The chemical formula for water is $H_2O$

Hence, the correct answer is Option C.

• For 4:

For the given options:

Polar covalent bond is formed when there is no difference in electronegativity between the atoms. For Example: $N_2,O_2$ etc..

Ionic bond is defined as the bond which is formed by complete transfer of electrons from one atom to another atom. The atom which looses the electron is known as electropositive atom and the atom which gains the electron is known as electronegative atom. This bond is usually formed between a metal and a non-metal.

Magnesium is a metal and oxygen is a non-metal. So, their ions gets attracted to each other leading to the formation of ionic compound having chemical formula MgO.

Hydrogen bond is defined as an intermolecular force having partial ionic-covalent character. H-bonding takes place between a hydrogen atom (attached with an electronegative atom e.g. O, N and F) and an electronegative atom (O,N and F).

Covalent bond is defined as the bond which is formed when sharing of electrons takes place between the atoms. This is usually formed between two non-metals.

Hence, the correct answer is Option B.