General Chemistry – Measurements, Atomic Structure & The Periodic Table

Flashcards covering key points from chapters on measurements, significant figures, scientific notation, conversion factors, density, temperature scales, and extensive material on atomic structure, isotopes, periodic law, electron configurations, and element classifications.

What is the fundamental reason scientists prefer the metric system over the English system?

Metric units relate to each other by powers of ten, making conversions simpler and less error-prone.

In the metric system, how many meters are in one kilometer?

1 km = 10³ m

Which metric prefix means one-billionth (10⁻⁹)?

nano- (n)

Which metric prefix represents 10⁶ (one million)?

mega- (M)

What is the base SI unit of mass?

gram (g)

Convert 2500 mg to grams.

2.5 g

Define mass.

The measure of the total quantity of matter in an object.

Define weight.

The force exerted on an object by gravity; it varies with location.

State the relationship between millilitres and cubic centimetres.

1 mL = 1 cm³

How many significant figures are in 0.03040?

4 significant figures

Identify the estimated digit in the measurement 56.00 g.

The last zero (hundredths place) is the estimated digit.

Rule for zeros at the beginning of a number (e.g., 0.0045)

Leading zeros are never significant; they only locate the decimal point.

Rule for zeros between non-zero digits (e.g., 101)

Confined zeros are always significant.

Rule for trailing zeros in 2500.

Trailing zeros without a decimal point are not significant.

When multiplying or dividing, how is the number of significant figures in the answer chosen?

It equals the fewest significant figures present in any factor.

When adding or subtracting, how is the precision of the answer set?

Round to the smallest number of decimal places present in any term.

Round 0.009876 to three significant figures.

0.00988

Express 43 000 in scientific notation with three significant figures.

4.30 × 10⁴

Convert 3.20 × 10⁻³ to decimal notation.

0.00320

Multiply (2.0 × 10²)(3.00 × 10³) and give the answer with correct sig figs.

6.0 × 10⁵

Define conversion factor.

A ratio that expresses how one unit of measurement relates to another.

Give the two reciprocal conversion factors derived from 60 s = 1 min.

60 s/1 min and 1 min/60 s

State the equality that defines the inch-centimetre relationship.

1 in. = 2.54 cm (exact)

Convert 15.0 inches to centimetres.

15.0 in × 2.54 cm/in = 38.1 cm

Outline the three steps of dimensional analysis.

1) Write the given quantity and desired units. 2) Multiply by conversion factors so units cancel. 3) Perform the math and check sig figs/units.

Calculate the density of a substance with mass 18.4 g and volume 20.0 mL.

Density = mass/volume = 0.920 g mL⁻¹

Would an object with density 0.79 g mL⁻¹ float or sink in water?

It would float (density < water’s 1.0 g mL⁻¹).

What is the formula for converting Celsius to Kelvin?

K = °C + 273

What is 98.6 °F in degrees Celsius?

(98.6 – 32)×5/9 = 37 °C

Freeze point of water on Kelvin scale.

273 K

Name the three subatomic particles.

Electron, proton, neutron

Charge and approximate relative mass of an electron.

Charge = –1; relative mass ≈ 1 (reference), actual 9.11 × 10⁻²⁸ g

Location of protons and neutrons in the atom.

In the nucleus.

Define atomic number (Z).

The number of protons in the nucleus of an atom; equals number of electrons in a neutral atom.

Define mass number (A).

Total number of protons plus neutrons in the nucleus.

Calculate neutrons: A = 23, Z = 11.

Neutrons = A – Z = 12

Write the complete chemical symbol for an atom with 9 protons and 10 neutrons.

¹⁹₉F

Define isotope.

Atoms of the same element (same Z) with different numbers of neutrons (different A).

Do isotopes have identical chemical properties? Why/why not?

Yes, because they have the same number of electrons/identical electron configurations.

Formula for weighted atomic mass.

Σ(isotopic mass × fractional abundance)

Why are atomic masses often non-integer values?

They are weighted averages of the masses of all naturally occurring isotopes.

State the modern periodic law.

When elements are arranged in order of increasing atomic number, elements with similar chemical properties recur periodically.

What is a period in the periodic table?

A horizontal row of elements.

What is a group (family) in the periodic table?

A vertical column of elements with similar chemical properties.

Group 1 elements are known as what?

Alkali metals (except H).

Group 17 elements are called?

Halogens.

Where are metals located on the periodic table?

To the left of the staircase line; majority of elements.

List general physical properties of metals.

Lustrous, good conductors of heat/electricity, malleable, ductile, usually solid.

Define electron shell.

A main energy level around the nucleus containing electrons with similar energy.

Maximum electrons in a shell (formula).

2n², where n = shell number.

Order the subshells by increasing energy within a shell.

s < p < d < f

How many orbitals in a p subshell?

3 orbitals (6 electrons max).

Shape of an s orbital.

Spherical.

Hund’s rule for orbital diagrams.

Electrons occupy degenerate orbitals singly with parallel spins before pairing.

Give the electron configuration of oxygen.

1s² 2s² 2p⁴

What is a distinguishing electron?

The last (highest-energy) electron added when building up an element's electron configuration; identifies its block (s,p,d,f).

Elements in the d block are classified as?

Transition elements.

Which subshell is being filled for lanthanides?

4f subshell (inner transition).

State Pauli Exclusion Principle.

No two electrons in an atom can have the same set of four quantum numbers; an orbital holds max two electrons with opposite spins.

Why is helium placed with noble gases though its distinguishing electron is s²?

It has a filled outer shell and exhibits chemical inertness like other noble gases.

Define representative element.

An s- or p-block element (Groups 1-2 and 13-18) that displays a wide range of properties.

Give the density equation.

Density = mass ÷ volume

If a 250-mL beaker holds 200 g of a liquid, what is the liquid’s density?

Density = 200 g / 250 mL = 0.80 g mL⁻¹

Unit-factor method is another name for what problem-solving technique?

Dimensional analysis.

Show one step to convert 25 °C to Kelvin.

K = 25 + 273 = 298 K

How many significant figures in 5.00 × 10⁻³ m?

Three significant figures

Explain why 60 s = 1 min has unlimited significant figures.

Because it is a defined (exact) relationship, not a measurement.

Give the dual conversion factor from 1 L = 1.06 qt (rounded).

1.06 qt/1 L and 1 L/1.06 qt

Name four specially-named groups and their group numbers.

Alkali metals (1), Alkaline earth metals (2), Halogens (17), Noble gases (18).

What orbital is filled after 4s according to the Aufbau order?

3d subshell.

Which has higher energy: 4s or 3d?

3d is higher than 4s.

How many unpaired electrons in a ground-state nitrogen atom?

3 unpaired electrons (2p³).

What is meant by ‘ground state’ of an atom?

Its electrons occupy the lowest-energy orbitals available.

State the density trend between solids, liquids, gases.

Typically: ρ (solids) > ρ (liquids) » ρ (gases), with exceptions like ice vs water or Hg(l).

Give the equation linking Fahrenheit and Celsius.

°F = (9/5)(°C) + 32

Convert –40 °C to Fahrenheit.

(–40×9/5)+32 = –40 °F (same value)

Classify Si: metal, non-metal, or metalloid?

Metalloid; but in the text, Si often treated as metalloid though in “nonmetal vs metal” section it fell among nonmetals middle of staircase.

Which family contains very unreactive gases?

Noble gases (Group 18).

Define nucleon.

A particle found in the nucleus; i.e., a proton or neutron.

Formula to find neutrons when atomic and mass numbers are known.

Neutrons = A – Z

Why does ¹⁴C behave chemically like ¹²C?

Because chemical behaviour depends on electrons, and isotopes have identical electron configurations.