Atomic Structure

Democritus named the smallest particles of matter __________ because they could not be divided.

Answer explanation

Democritus derived his term from the Greek word atomos.

Tags

NGSS.MS-PS1-1

Dalton's theory suggests that all matter is made up of individual particles called __________, which cannot be divided.

Answer explanation

Dalton borrowed his idea of atoms from Democritus, but stated that there were rules to how these atoms operated.

Tags

NGSS.MS-PS1-1

Which of the sentences below does not represent main points of Dalton's theory of atoms.

• All elements are composed of atoms.

• In a particular compound, atoms of different elements always combine the same way.

• All atoms have the same mass.

Answer explanation

John Dalton didn't understand how atoms were made up of different amounts and types of particles that each had their own masses.

Tags

NGSS.MS-PS1-1

Objects with like electric charges __________.

• attract

• repel

• reflect

• deflect

Answer explanation

This idea was used by J.J. Thomson when he developed his plum pudding model, stating that negatively charged electrons were kept together by being suspended in a positively charged substance in an atom.

Tags

NGSS.MS-PS2-3

Objects with opposite electric charges __________.

• attract

• repel

• reflect

• deflect

Answer explanation

This idea was used by J.J. Thomson when he developed his plum pudding model, stating that negatively charged electrons were kept together by being suspended in a positively charged substance in an atom.

Tags

NGSS.MS-PS2-3

NGSS.MS-PS2-5

Thomson concluded that the particles in the glowing beam had a(n)  __________ charge because they were attracted to a positive plate.

Answer explanation

Scientists already understood that like charges repel and opposite charges attract.

Tags

NGSS.MS-PS2-5

Which of the sentences below does not describe Thomson's model of the atom.

• An atom is filled with positive matter.

• An atom is mostly space with a small nucleus.

• Negative charges are scattered throughout an atom.

Answer explanation

Ernest Rutherford, a student of J.J. Thomson, is the scientist who stated that the center of an atom is called a nucleus.

Tags

NGSS.MS-PS1-1

This model is used today for studying atoms.

• Dalton

• Thomas

• Rutherford

• Bohr

Answer explanation

This scientist said that electrons orbit the nucleus like planets around a sun.

Tags

NGSS.MS-PS1-1

J.J. Thomson’s experiments provided the first evidence of __________.

• atoms

• a nucleus

• subatomic particles

• elements

Answer explanation

Prior to Thomson's discovery, scientists thought that an atom could not be broken down any further.

Tags

NGSS.MS-PS1-1

The concept of an atom as a small particle of matter that cannot be divided was proposed by the ancient Greek philosopher, Democritus.

• True

• False

Answer explanation

The Greek word for "uncut" or "indivisible" is atomos.