Atomic Theory Quiz

Who proposed the first modern atomic theory?

• Albert Einstein

• John Dalton

• Isaac Newton

• Niels Bohr

Answer explanation

John Dalton proposed the first modern atomic theory in the early 19th century, establishing that matter is made up of atoms, which are indivisible and combine in fixed ratios to form compounds.

According to Dalton, matter is made up of tiny particles called:

• molecules

• ions

• electrons

• atoms

Answer explanation

According to Dalton's atomic theory, matter is composed of tiny indivisible units called atoms. This distinguishes atoms from larger structures like molecules and ions, making 'atoms' the correct answer.

Dalton believed that atoms are:

• indivisible

• made of smaller parts

• visible under a microscope

• always charged

Answer explanation

Dalton's atomic theory stated that atoms are indivisible, meaning they cannot be broken down into smaller parts. This belief was foundational in the development of modern chemistry, making 'indivisible' the correct choice.

Which statement matches Dalton’s theory?

• Atoms can be created in chemical reactions.

• Atoms are simply rearranged in chemical reactions.

• Atoms are destroyed when burned.

• Atoms disappear when mixed.

Answer explanation

Dalton's theory states that atoms are not created or destroyed in chemical reactions; they are simply rearranged. Therefore, the correct statement is that atoms are simply rearranged in chemical reactions.

A compound is formed when:

• electrons are shared

• only one type of atom is used

• two or more different kinds of atoms combine

• neutrons are removed

Answer explanation

A compound is formed when two or more different kinds of atoms combine. This distinguishes compounds from elements, which consist of only one type of atom. Sharing electrons can occur in compounds, but the key is the combination of different atoms.

Which of the following is a compound?

• Hydrogen fluoride

• Gold

• Oxygen gas

• Carbon

Answer explanation

Hydrogen fluoride is a compound made of hydrogen and fluorine atoms. In contrast, gold and carbon are elements, while oxygen gas (O2) is a diatomic molecule, not a compound.

What did Dalton believe about atoms of the same element?

• They have different properties

• They are identical

• They do not form compounds

• They are unstable

Answer explanation

Dalton believed that atoms of the same element are identical in mass and properties. This means they share the same characteristics, which is why the correct answer is 'They are identical.'

What happens to atoms during a chemical reaction?

• They melt

• They disappear

• They rearrange

• They gain weight

Answer explanation

During a chemical reaction, atoms do not melt, disappear, or gain weight. Instead, they rearrange to form new substances, which is the essence of chemical reactions.

Which element was used as an example that combines with hydrogen to form ammonia?

• Oxygen

• Fluorine

• Nitrogen

• Carbon

Answer explanation

Nitrogen is the element that combines with hydrogen to form ammonia (NH3). Unlike oxygen, fluorine, or carbon, nitrogen is essential in this process, making it the correct choice.

What is the correct combination of atoms in baking soda (sodium bicarbonate)?

• 2 sodium, 2 hydrogen

• 1 sodium, 1 hydrogen, 1 carbon, 3 oxygen

• 1 hydrogen, 1 oxygen

• 2 carbon, 3 oxygen

Answer explanation

Baking soda, or sodium bicarbonate, has the chemical formula NaHCO3. This means it contains 1 sodium (Na), 1 hydrogen (H), 1 carbon (C), and 3 oxygen (O) atoms, making the correct choice 1 sodium, 1 hydrogen, 1 carbon, 3 oxygen.