Chapter 1–7 Review: Atoms, Elements, Molecules, and Atomic Theory

A set of concept-check questions covering matter, atoms, elements, molecules vs. compounds, Dalton’s atomic theory, subatomic particles, Rutherford and Millikan experiments, nucleus vs. electron cloud, periodic table, natural vs. synthetic elements, Avogadro’s number, and basic charge interactions. These flashcards target the key ideas from Chapters 1–7 of the notes.

What is matter?

Anything that can be seen, touched, felt, or smelled; it is composed of atoms.

What are atoms?

The tiny building blocks of matter; they exist in different forms and connections that make all substances.

What is an element?

A substance defined by the type of atom it contains; elements are organized on the periodic table.

What is the periodic table and who created it?

A table organizing elements by properties and periodicity; created by Dmitri Mendeleev.

What is a molecule?

Two or more atoms joined together chemically, by covalent or ionic bonds.

What is a compound?

Two or more different atoms bonded together in a definite, simple whole-number ratio; e.g., H2O is a compound, H2 is not.

What are Dalton's four postulates of atomic theory?

1) All matter is composed of atoms; 2) Atoms of a given element are identical; 3) Atoms combine in simple whole-number ratios to form compounds; 4) Atoms are indivisible in chemical reactions and cannot be created or destroyed.

What is the nucleus?

The center of the atom that contains protons and neutrons and holds most of the atom’s mass; surrounded by the electron cloud.

What are protons?

Positively charged subatomic particles located in the nucleus; contribute to atomic mass and positive charge.

What are neutrons?

Electrically neutral subatomic particles in the nucleus; contribute mass but have no charge.

What are electrons?

Negatively charged subatomic particles that orbit the nucleus in the electron cloud; very light and fast.

How does electron mass compare to proton/neutron mass?

Electron mass is extremely small; protons and neutrons account for most of an atom’s mass.

What is the electron charge-to-mass ratio and who determined it?

The charge-to-mass ratio of the electron was determined from Thomson’s experiments; a later oil-drop experiment refined the understanding of electron charge and mass.

What was Millikan’s oil-drop experiment about?

Aimed to measure the elementary charge by balancing gravity and electrostatic forces on oil droplets; showed charge is quantized and allowed calculation of electron charge (and mass via charge-to-mass ratio).

What is the Plum Pudding model?

An early atomic model proposing a positively charged 'pudding' with negatively charged electrons embedded in it; later disproven by Rutherford.

What did Rutherford’s gold foil experiment reveal?

Most alpha particles passed through, some were deflected; indicated a small, dense nucleus containing positive charge within mostly empty space.

What did the nuclear (Rutherford) model establish about atoms?

Atoms have a tiny, massive nucleus with protons (and later neutrons) and an electron cloud surrounding it; most of the atom’s mass is in the nucleus; most of the atom is empty space.

How many elements occur naturally vs are synthetic?

About 92 elements occur naturally; the rest have been synthetic (made in laboratories) or discovered in other contexts.

What is Avogadro’s number and what does it define?

6.022 × 10^23; the number of particles in one mole, used to count atoms and molecules.

What is a mole?

A unit that contains 6.022 × 10^23 particles; used to relate mass to the number of atoms or molecules.

What is the relationship between charges in atoms and common compounds like NaCl?

Opposite charges attract (electrostatic attraction) and like charges repel; in NaCl, Na+ and Cl− are held together by attraction, giving a neutral compound.

Where is most of an atom’s mass located and what about the size of the nucleus relative to the atom?

Most of the mass is in the nucleus (protons and neutrons); the nucleus is tiny compared to the overall size of the atom, which is mostly empty space occupied by the electron cloud.