Periodic Table Practice Questions
20 free Periodic Table practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which scientist is credited with arranging the first periodic table based on increasing atomic mass and leaving gaps for undiscovered elements?
- A Henry Moseley
- B Dmitri Mendeleev
- C John Dalton
- D Ernest Rutherford
Correct answer: Dmitri Mendeleev
Dmitri Mendeleev published the first widely recognized periodic table in 1869. His genius lay in predicting the properties of elements like gallium and germanium before they were even discovered.
Elements in the same vertical column of the periodic table are called a 'group' or 'family'. What do they primarily have in common?
- A The same number of electron shells
- B The same atomic mass
- C The same number of valence electrons
- D The same physical state at room temperature
Correct answer: The same number of valence electrons
Elements in the same group possess the same number of electrons in their outermost shell. This similarity in valence electron configuration results in very similar chemical reactivity and bonding characteristics.
Which of the following elements is classified as a metalloid (semimetal)?
- A Aluminum
- B Silicon
- C Phosphorus
- D Sulfur
Correct answer: Silicon
Silicon is a classic metalloid located along the 'stair-step' line of the periodic table. It exhibits properties of both metals and non-metals, making it an essential semiconductor in electronics.
As you move from left to right across a period in the periodic table, what generally happens to the atomic radius?
- A It increases
- B It decreases
- C It remains constant
- D It increases then decreases
Correct answer: It decreases
Moving across a period, the number of protons increases, which increases the effective nuclear charge. This stronger positive pull draws the electrons closer to the nucleus, effectively shrinking the atomic radius.
Which group of elements is known for being extremely unreactive due to having a full complement of valence electrons?
- A Alkali metals
- B Halogens
- C Noble gases
- D Alkaline earth metals
Correct answer: Noble gases
Noble gases (Group 18) have a complete octet of electrons (or a duet for Helium). This stable electron configuration makes them chemically inert under most standard conditions.
Which element has the highest electronegativity on the Pauling scale?
- A Oxygen
- B Chlorine
- C Fluorine
- D Cesium
Correct answer: Fluorine
Fluorine is the most electronegative element because it has a high effective nuclear charge and a small atomic radius. It has the strongest tendency to attract shared electrons in a chemical bond.
The horizontal rows of the periodic table are known as periods. What does the period number indicate about the atoms in that row?
- A The number of protons
- B The outermost electron shell
- C The total number of electrons
- D The number of isotopes
Correct answer: The outermost electron shell
The period number corresponds to the principal quantum number ($n$) of the outermost electrons. For example, elements in Period 4 have their valence electrons in the fourth energy shell.
Which of the following is a characteristic property of Alkali metals (Group 1)?
- A High density and hardness
- B They are found freely in nature
- C They react violently with water
- D They form ions with a -1 charge
Correct answer: They react violently with water
Alkali metals are highly reactive because they have only one valence electron that is easily lost. When placed in water, they react to form hydrogen gas and metal hydroxides, often with explosive force.
In the modern periodic table, elements are arranged in order of increasing:
- A Atomic mass
- B Atomic number
- C Density
- D Abundance in Earth's crust
Correct answer: Atomic number
Following the work of Henry Moseley, the periodic table was reorganized by atomic number (number of protons). This resolved discrepancies found in Mendeleev's mass-based arrangement, such as the placement of Argon and Potassium.
Which block of the periodic table contains the transition metals?
- A s-block
- B p-block
- C d-block
- D f-block
Correct answer: d-block
Transition metals occupy Groups 3 through 12, which correspond to the d-block. In these elements, the d-subshells are being filled with electrons.
What happens to the first ionization energy as you move down a group?
- A It increases
- B It decreases
- C It remains the same
- D It fluctuates randomly
Correct answer: It decreases
As you move down a group, the valence electrons are further from the nucleus and are shielded by more inner electron shells. This reduces the electrostatic attraction, making it easier (requiring less energy) to remove an electron.
Which of the following elements is a liquid at room temperature (25°C)?
- A Mercury
- B Gallium
- C Magnesium
- D Iodine
Correct answer: Mercury
Mercury (Hg) and Bromine (Br) are the only two elements on the periodic table that are liquid at standard room temperature and pressure. Mercury is the only metal that is liquid under these conditions.
The 'Halogens' are located in which group of the periodic table?
- A Group 1
- B Group 2
- C Group 17
- D Group 18
Correct answer: Group 17
Group 17 contains the Halogens, including Fluorine, Chlorine, Bromine, and Iodine. These are highly reactive non-metals that need only one more electron to achieve a stable noble gas configuration.
Where are the 'Lanthanides' and 'Actinides' usually located on a standard periodic table layout?
- A In the first two columns
- B Along the metalloid staircase
- C Two rows below the main table
- D Integrated into the p-block
Correct answer: Two rows below the main table
These elements, known as the inner transition metals or f-block elements, are placed below the main body of the table. This is done to prevent the table from becoming too wide and to keep the other groups aligned.
Which element is the most abundant metal in the Earth's crust?
- A Iron
- B Aluminum
- C Copper
- D Gold
Correct answer: Aluminum
Aluminum is the most abundant metal and the third most abundant element in the Earth's crust. It is primarily found in the form of bauxite ore rather than as a pure metal.
Elements that are poor conductors of heat and electricity and are generally brittle in solid form are known as:
- A Metals
- B Non-metals
- C Alloys
- D Lanthanides
Correct answer: Non-metals
Non-metals are located on the right side of the periodic table. Unlike metals, they lack luster, have lower melting points, and do not have free-moving electrons to conduct heat or electricity effectively.
Which element belongs to the 'Alkaline Earth Metals' group?
- A Sodium
- B Calcium
- C Iron
- D Silver
Correct answer: Calcium
Calcium is in Group 2, the Alkaline Earth Metals. These elements have two valence electrons and are very reactive, though slightly less so than the Group 1 alkali metals.
The energy change that occurs when an electron is added to a neutral atom in the gaseous state is called:
- A Ionization Energy
- B Electronegativity
- C Electron Affinity
- D Activation Energy
Correct answer: Electron Affinity
Electron affinity measures the attraction an atom has for an additional electron. Most non-metals have highly negative electron affinities, meaning they release energy when they gain an electron.
Which of the following elements is a diatomic gas at room temperature?
- A Helium
- B Bromine
- C Oxygen
- D Argon
Correct answer: Oxygen
Oxygen exists as O2, one of the seven diatomic elements (H, N, O, F, Cl, Br, I), and it is a gas at room temperature. Helium and argon are noble gases that exist as single, unbonded atoms, while bromine is diatomic but is a liquid under ordinary conditions.
Which element has the atomic number 1?
- A Beryllium
- B Hydrogen
- C Lithium
- D Oxygen
Correct answer: Hydrogen
Hydrogen is the first element on the periodic table, consisting of one proton and one electron. It is unique because it doesn't fit perfectly into any single chemical group.