Lecture on Atoms, Molecules, and Atomic Theory

These flashcards cover key concepts related to atoms, molecules, atomic theory, and energy changes in bonding.

What is the smallest unit of an element?

An atom.

What is a molecule?

A group of two or more atoms connected to make a separate substance.

How does an element differ from a compound?

An element consists of a collection of the same type of atoms, while a compound is formed from two or more different types of atoms combined.

What evidence supports the existence of atoms?

Advancements in technology, such as atomic force microscopy, allow us to physically see atoms.

Who discovered the electron, and how?

J.J. Thomson discovered the electron through experiments with a cathode ray tube.

What did Rutherford conclude from his gold foil experiment?

He concluded that most of an atom is empty space and that there is a dense, positively charged nucleus.

What is the Plum Pudding Model?

Thomson's model of an atom as a positively charged sphere with electrons embedded in it.

How does the scientific theory differ from everyday use of the term 'theory'?

A scientific theory is a well-substantiated explanation based on evidence, while everyday theories are often just personal opinions or guesses.

As two isolated atoms approach each other, what forces are involved?

Electrostatic forces attract them, while repulsive forces arise when they get too close.

What happens to kinetic energy as two helium atoms approach each other?

Kinetic energy increases due to the attractive electrostatic force.

What is London Dispersion Force (LDF)?

A weak force that occurs between all atoms and molecules due to temporary dipoles.

How do covalent bonds differ from London Dispersion Forces?

Covalent bonds involve sharing of electron pairs and form strong, stable bonds, while LDFs are weak, transient forces.

What is the relationship between the size of an electron cloud and London Dispersion Forces?

The larger the electron cloud, the stronger the London Dispersion Forces.

What energy change occurs when covalent bonds form?

Potential energy decreases because the atoms share electrons, resulting in a more stable configuration.

What happens to kinetic energy when LDFs form between two atoms?

Kinetic energy decreases as the repulsive force dominates, causing the atoms to slow down.