Chemistry

Periodic Classification and Elements

1,092 Questions

Periodic classification organizes chemical elements based on atomic structure, periodic laws, and elemental properties. It covers historical classification systems, electron configurations, and periodic trends. Test takers preparing for chemistry sections will find these questions crucial for mastering fundamental element properties and atomic interactions.

Periodic table structureAtomic orbitalsElement identificationPeriodic laws

Periodic Classification and Elements Questions

Multiple choice

_______ are naturally occurring atoms on Earth.

  1. Organs

  2. Elements

  3. Molecules

  4. People
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Elements are pure substances consisting of only one type of atom. They occur naturally on Earth and are the simplest forms of matter.

Multiple choice

Atoms are the building blocks of _______.

  1. matter

  2. elements

  3. life

  4. Earth
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Atoms are the fundamental building blocks of all matter. While they make up life and elements, matter is the most encompassing category.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

According to Werner’s theory of valency transition metals possesses:

  1. only one type of valency

  2. two types of valencies

  3. three types of valencies

  4. four types of valencies
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Werner’s theory of valence, transition metals has two valencies are primary valencies and secondary valency.
Primary valencies are those which are statisfied by ligands through coordination bonds and charge that remained on the coordination sphere is satisfied by secondary valence.


Hence, the correct option is $B$

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Secondary valencies correspond to ____________ of the metal atom and are satisfied by ligands.

  1. coordination number

  2. valency

  3. element

  4. molecules
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 Secondary valency corresponds to the coordination number of central metal atom or ion. This may be satisfied by either negative ions or neutral molecules called ligands.

 Ligands satisfying the secondary valencies are always shown in square brackets, i.e. they form the coordination sphere of the metal atom.


Hence,option A is correct.

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

Some of the following properties are important in determining whether an element has metallic properties.
I : atomic number
II : atomic weight
III: number of valence electrons
IV: number of vacant atomic orbitals
V: total number of electronic shells in the atom
Select correct properties from the codes given below:

  1. I, II, III, IV

  2. I, III, IV, V

  3. III, IV

  4. III, IV, V
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The following properties are important in determining whether an element has metallic properties.
III: number of valence electrons
IV: number of vacant atomic orbitals
All metals are electropositve elements and have a tendency to lose electrons.  Alkali metals and alkaline earth metals contain one and two valence electrons respectively.They readily lose these electrons and show metallic properties. Transition metals have a number of vacant d orbitals and show variable valency. Due to the presence of vacant d orbitals, they show variable valence.

Multiple choice chemistry particle nature, basic units history of atomic model atomic theory of dalton daltons atomic theory

The valence electrons of an element are responsible for :

  1. physical properties of an element

  2. chemical properties of an element

  3. Both A and B

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Valence electrons are electrons in the outermost shell and they are responsible for determining the number of bond formation and an atoms charge.This give the atom its chemical properties.

Multiple choice chemistry nitrogen and sulfur ammonia and fertilizers preparation of ammonia-laboratory method and haber's process ammonia

An element X combines with hydrogen to form a compound $NH _3$. The element X is placed on the right side of the periodic table. What is true about the element X?
(a) Has $3$ valence electrons
(b) Is a metal and is solid
(c) Is a non-metal and is a gas
(d) Has $5$ valence electrons
(e) $NH _3$ reacts with water to form a basic compound.

  1. (a), (b) and (c)

  2. (b), (c) and (d)

  3. (c), (d) and (e)

  4. (e), (a) and (b)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

X is N because it is placed on the right side of the periodic table & compound is $NH _3$. X is a non metal and valence electrons are $5$ & $NH _3+H _2O\rightarrow NH _4OH$(Base)

Multiple choice

What is the general trend in atomic size across a period in the periodic table?

  1. Increases

  2. Decreases

  3. Remains constant

  4. Varies irregularly
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Atomic size generally decreases across a period from left to right due to increasing nuclear charge and the same number of electron shells.

Multiple choice

Which of the following is an example of a main group element?

  1. Sodium

  2. Magnesium

  3. Aluminum

  4. Iron
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sodium is a main group element, also known as an alkali metal, characterized by its one valence electron.

Multiple choice

The Pauli exclusion principle states that:

  1. No two electrons in an atom can have the same set of quantum numbers.

  2. No two electrons in an atom can have the same spin.

  3. No two electrons in an atom can have the same energy.

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The Pauli exclusion principle states that no two electrons in an atom can have the same set of quantum numbers, which includes spin, energy, and orbital.

Multiple choice

The Hartree-Fock method is a:

  1. Self-consistent field method

  2. Ab initio method

  3. Semi-empirical method

  4. Density functional theory method
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Hartree-Fock method is a self-consistent field method that approximates the wave function of a many-electron system as a product of one-electron wave functions.

Multiple choice

The density functional theory (DFT) method is based on:

  1. The electron density

  2. The wave function

  3. The energy of the system

  4. The Hamiltonian operator
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Density functional theory (DFT) is a method for calculating the electronic structure of atoms, molecules, and solids based on the electron density.

Multiple choice

What is the abundance of light elements?

  1. The relative abundance of hydrogen and helium in the universe.

  2. The relative abundance of carbon and oxygen in the universe.

  3. The relative abundance of nitrogen and neon in the universe.

  4. The relative abundance of silicon and iron in the universe.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The abundance of light elements is the relative abundance of hydrogen and helium in the universe. It is a key piece of evidence for the Big Bang Theory.

Multiple choice

What is the order of an element in a group?

  1. The number of elements in the group

  2. The number of times the element appears in the group
  3. The smallest positive integer $n$ such that $a^n = e$, where $e$ is the identity element of the group
  4. The largest positive integer $n$ such that $a^n = e$, where $e$ is the identity element of the group

  5. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The order of an element in a group is the smallest positive integer $n$ such that $a^n = e$, where $e$ is the identity element of the group.

Multiple choice

What is the 18-electron rule?

  1. The rule that states that a metal complex is stable when it has 18 electrons in its valence shell.

  2. The rule that states that a metal complex is stable when it has 12 electrons in its valence shell.

  3. The rule that states that a metal complex is stable when it has 6 electrons in its valence shell.

  4. The rule that states that a metal complex is stable when it has 2 electrons in its valence shell.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The 18-electron rule states that a metal complex is stable when it has 18 electrons in its valence shell.