Unit 1: Early Theories of Matter, Periodic Table, Atomic Structure & Mass

Flashcards testing knowledge of atomic history, periodic table organization, subatomic particles, isotope notation, and atomic mass calculations.

Who was the first person to propose the idea that matter is not divisible?

Democritus (460 BC)

What were Democritus's key proposals regarding the atom?

Democritus proposed that matter is made of atoms, which cannot be created, destroyed, or further divided, and that atoms come in different sizes, shapes, and properties.

What are the four points of John Dalton's Atomic Theory (1803)?

1) All matter is composed of atoms. 2) All atoms of an element are identical. 3) Atoms cannot be created, divided into smaller particles, or destroyed. 4) Different elements have atoms of different size and mass.

What is the definition of an atom?

The smallest particle of an element that still retains the properties of the element.

How does the number of atoms in a penny compare to the 2022 world population according to the notes?

The world population in 2022 was $7,800,000,000$, whereas a single penny contains $29,000,000,000,000,000,000,000$ atoms.

Who discovered the electron in 1897 and debunked Dalton's Atomic Theory?

JJ Thomson

What experiment did JJ Thomson conduct to discover the electron?

The Cathode ray tube experiment

What is JJ Thomson's Plum Pudding Model?

A model of the atom describing negatively charged particles (electrons) surrounded by a volume of positive charge.

What setup was used in Ernest Rutherford's 1909 Gold Foil Experiment?

An alpha particle source inside a lead block aiming alpha particles at a thin gold leaf surrounded by a zinc sulphide screen, all inside a vacuum.

What were the three major conclusions of Rutherford's Gold Foil Experiment?

a) The atom is mostly empty space. b) The atom has a small, dense, positive center (nucleus). c) Alpha particles are deflected if they pass close enough to this center.

What regions and particles make up the modern view of the atom shown in this diagram?

The atom consists of two regions: the nucleus (containing protons and neutrons) and the surrounding electron cloud (containing electrons).

What are the location, relative electrical charge, and actual mass of an electron?

Location: Electron cloud; Relative charge: $-1$; Actual mass: $9.11 \times 10^{-28}\,\text{g}$.

What are the location, relative electrical charge, and actual mass of a proton?

Location: Nucleus; Relative charge: $+1$; Actual mass: $1.673 \times 10^{-24}\,\text{g}$.

What are the location, relative electrical charge, and actual mass of a neutron?

Location: Nucleus; Relative charge: $0$; Actual mass: $1.675 \times 10^{-24}\,\text{g}$.

What five pieces of information does the Periodic Table provide for elements?

Atomic Symbol (1-2 letters), Atomic Mass/Weight, Atomic Number, Groups (columns), and Families or Periods (rows).

How are columns and rows organized on the periodic table?

Columns are called Groups (numbered $1$ to $18$) and rows are called Periods (numbered $1$ to $7$).

What are the key properties of metals according to the notes?

Located to the left of the darkened staircase; conduct heat and electricity; malleable (can be hammered into thin sheets); ductile (can be pulled into wire); lustrous (shiny); mainly solid at room temperature.

What are the key properties of nonmetals?

Located in the upper-right corner; brittle; poor conductors of heat and electricity; dull; may be solid, liquid, or gas at room temperature.

What are the characteristics of the 7 metalloids (semimetals)?

Close to the staircase; mixed properties; solid under standard conditions; metallic luster; brittle; semiconductors.

What fundamental relationship links atomic number, protons, and electrons in a neutral atom?

$$\text{Atomic Number} = \text{number of protons} = \text{number of electrons}$$

What is the formula to calculate the number of neutrons in an atom?

$$\text{Number of Neutrons} = \text{Mass Number} - \text{Number of Protons}$$

What defines isotopes of an element?

Elements with different mass numbers (different number of neutrons), but the same atomic number, number of protons, and number of electrons.

According to this diagram, how do Lithium-7 (Li-7) and Lithium-6 (Li-6) differ in subatomic structure?

Both have $3$ protons and $3$ electrons, but Lithium-7 has $4$ neutrons while Lithium-6 has $3$ neutrons.

How do Atomic Number, Atomic Mass/Weight, and Mass Number differ in their definition, values, and units?

Atomic Number is the total number of protons (whole number, no unit); Atomic Mass/Weight is the weighted average of naturally occurring isotopes (decimal value in $\text{amu}$); Mass Number is the weight of the nucleus for a single atom ($p^+ + n^0$, whole number in $\text{amu}$).

What are the specific roles of protons, neutrons, and electrons within an atom?

Protons determine the identity of the atom; Neutrons hold together the nucleus; Electrons are responsible for chemical reactions.

What equation is used to calculate the atomic mass of an element from its isotopes?

$\text{Atomic Mass} = (RA_1 \times M_1) + (RA_2 \times M_2) + \dots$ where $RA$ is relative abundance as a decimal and $M$ is isotopic mass.

If Silicon exists as Si-28 ($92\%$), Si-29 ($5.0\%$), and Si-30 ($3.0\%$), what equation sets up its relative atomic mass calculation?

$$\text{Atomic Mass} = (0.92 \times 28) + (0.050 \times 29) + (0.030 \times 30)$$

Chlorine exists as $75\%$ chlorine-35 and $25\%$ chlorine-37. What is its calculated atomic mass?

$$\text{Atomic Mass} = (0.75 \times 35) + (0.25 \times 37) = 35.5\,\text{amu}$$

Boron has two isotopes: boron-10 (abundance = $19.8\%$, mass = $10.013\,\text{amu}$) and boron-11 (abundance = $80.2\%$, mass = $11.009\,\text{amu}$). What is the calculated atomic mass of boron?

$$\text{Atomic Mass} = (0.198 \times 10.013\,\text{amu}) + (0.802 \times 11.009\,\text{amu}) = 10.812\,\text{amu}$$