Chapter 2: Atoms and Elements — Review Flashcards

Flashcards covering laws of matter, atomic theory, isotopes and ions, atomic structure, the mole, and periodic table basics from the lecture notes.

What does the Law of Conservation of Mass state?

In a chemical reaction, matter is neither created nor destroyed.

What does the Law of Definite Proportions state?

All samples of a given compound have the same proportions of their constituent elements, regardless of source or preparation.

What does the Law of Multiple Proportions state?

When two elements form two compounds, the masses of the second element that combine with 1 g of the first element are in small whole-number ratios (e.g., AB1, AB2, AB3).

Name one postulate from Dalton’s Atomic Theory.

Elements are composed of tiny, indestructible particles called atoms.

According to Dalton, how do atoms of a given element compare?

All atoms of a given element have the same mass and other properties that distinguish them from atoms of other elements.

In chemical reactions, do atoms change into different elements?

No — atoms rearrange the way they are bound; they do not change into other elements.

What is the Plum Pudding model?

Thomson’s model where electrons are embedded in a positively charged sphere.

What did Rutherford’s Gold Foil Experiment demonstrate?

The existence of a small, dense nucleus containing most of the atom’s mass and positive charge; atoms are mostly empty space.

What particles are in the atomic nucleus?

Protons and neutrons.

What does the symbol Z represent in atomic notation?

The atomic number; the number of protons in the nucleus.

In a neutral atom, how do the numbers of electrons and protons relate?

They are equal.

What are isotopes?

Atoms of the same element with different numbers of neutrons (different mass numbers) but the same number of protons.

What does natural abundance refer to?

The percentage of each isotope of an element found in nature.

What is atomic mass?

The weighted average mass of all isotopes of an element according to their natural abundances.

If A is the mass number and Z is the atomic number, how many neutrons does an isotope have?

Neutrons = A − Z.

What is a monatomic ion?

An ion consisting of a single atom with a net charge.

What is a polyatomic ion?

An ion composed of two or more atoms bonded together with a net charge.

What is a cation?

A positively charged ion.

What is an anion?

A negatively charged ion.

Give an example of a monatomic cation and a polyatomic anion.

Example: Na+ (monatomic cation) and OH− (polyatomic anion).

What is Avogadro’s number?

6.022 × 10^23, the number of particles in one mole.

What is a mole?

The amount of substance containing 6.022 × 10^23 particles.

What is the relationship between molar mass and atomic mass?

The molar mass (g/mol) is numerically equal to the atomic mass (amu) for an element.

What is the mass of 1 mole of carbon atoms?

12.00 g C per mole of carbon atoms.

How do you convert mass to moles?

Divide the mass (g) by the element’s molar mass (g/mol).

How do you convert moles to atoms?

Multiply the number of moles by Avogadro’s number (6.022 × 10^23 atoms/mol).

What is the molar mass of copper (Cu)?

63.55 g/mol (63.55 g per mole).

What is the approximate atomic mass of copper given its isotopes Cu-63 and Cu-65 with natural abundances 69.17% and 30.83%?

Approximately 63.55 amu (weighted average of isotopes).

Where are metals located on the periodic table, and what are some of their common properties?

Left side and middle; good conductors of heat/electricity, malleable, ductile, shiny, and tend to lose electrons.

Where are nonmetals located, and how do they tend to behave chemically?

Upper right side of the periodic table; poor conductors, not ductile or malleable, and they tend to gain electrons.

What are metalloids and where are they found on the periodic table?

Elements along the zigzag line between metals and nonmetals; have mixed properties and can be semiconductors.

What are the three major divisions of the periodic table?

Metals, nonmetals, and metalloids.