Unit 2 PreTest

Front

Which scientist developed the atomic theory?

Back

John Dalton

Answer explanation

John Dalton is credited with developing the atomic theory in the early 19th century, proposing that matter is made up of atoms, which are indivisible and combine in fixed ratios to form compounds.

Front

Which scientist developed the atomic theory?

Back

John Dalton

Answer explanation

John Dalton is credited with developing the atomic theory in the early 19th century, proposing that matter is made up of atoms, which are indivisible and combine in fixed ratios to form compounds.

Front

He developed the planetary model of the atom.

Back

Bohr

Answer explanation

The planetary model of the atom, which describes electrons orbiting the nucleus, was developed by Niels Bohr. Rutherford proposed the nuclear model, while Chadwick discovered the neutron and Dalton formulated atomic theory.

Front

James Chadwick discovered the ________.

Back

neutron

Answer explanation

James Chadwick discovered the neutron in 1932, which is a subatomic particle found in the nucleus of an atom. This discovery was crucial for understanding atomic structure and led to advancements in nuclear physics.

Front

What did Thomson discover?

Back

electron

Answer explanation

Thomson discovered the electron in 1897 through his experiments with cathode rays, demonstrating that they were composed of negatively charged particles, which he named electrons.

Front

Subatomic particles with a negative charge

Back

Electrons

Answer explanation

Electrons are subatomic particles that carry a negative charge, distinguishing them from protons, which are positively charged, and neutrons, which have no charge. Quarks also have fractional charges but are not classified as negatively charged particles.

Front

Subatomic particles with a positive charge

Back

protons

Answer explanation

Protons are subatomic particles that carry a positive charge, distinguishing them from neutrons, which are neutral, and isotopes, which refer to variations of elements. Atomic mass is a measure, not a particle.

Front

Subatomic particles that are neutral in charge

Back

Neutrons

Answer explanation

Neutrons are subatomic particles that have no electric charge, making them neutral. In contrast, protons are positively charged, electrons are negatively charged, and the nucleus is the center of an atom containing protons and neutrons.

Front

A tiny but very dense, positively charged portion of the atom that holds most of the atomic mass.

Back

Nucleus

Answer explanation

The nucleus is a tiny, dense, positively charged part of the atom that contains most of its mass, distinguishing it from electron shells, orbitals, and the electron cloud, which do not hold significant mass.

Front

Where are electrons likely to be found as they travel around the nucleus?

Back

Electron Cloud

Answer explanation

Electrons are likely to be found in the Electron Cloud, which is the region around the nucleus where they are most probable to exist. They are not found within protons or neutrons, which are located in the nucleus.