chem units 3 and 4 b

What are the three main subatomic particles?

Protons, neutrons, and electrons.

Where are protons located?

In the nucleus.

Where are neutrons located?

In the nucleus.

Where are electrons located?

In orbitals around the nucleus.

What is the charge of a proton?

+1.

What is the charge of a neutron?

0 (neutral).

What is the charge of an electron?

−1.

What is the approximate mass of a proton?

1 amu.

What is the approximate mass of a neutron?

1 amu.

What is the approximate mass of an electron?

Approximately 0 amu; its actual mass is much smaller.

What is the nucleus?

The dense, positively charged center of an atom.

Where is most of an atom's mass concentrated?

In its nucleus.

Why is an atom mostly empty space?

The nucleus occupies a tiny region compared with the atom's overall size.

What is an atom?

The smallest unit of an element that retains its chemical identity.

What is an element?

A substance whose atoms all have the same number of protons.

What is an ion?

An atom or group of atoms with a net electric charge.

What is a cation?

A positively charged ion formed by losing electrons.

What is an anion?

A negatively charged ion formed by gaining electrons.

What determines an element's identity?

Its number of protons.

What is atomic number?

The number of protons in an atom's nucleus.

How do you calculate mass number?

Mass number = protons + neutrons.

How do you calculate neutrons?

Neutrons = mass number − atomic number.

How do you calculate the charge of an atom or ion?

Charge = number of protons − number of electrons.

How many electrons does a neutral atom have?

The same number as protons.

How do you find protons from isotope notation?

Read the atomic number; it equals the number of protons.

How do you find neutrons from isotope notation?

Subtract the atomic number from the mass number.

How do you find electrons in a positive ion?

Electrons = protons − positive charge magnitude.

How do you find electrons in a negative ion?

Electrons = protons + negative charge magnitude.

What does isotope notation show?

Element symbol, mass number, and atomic number; charge may also be shown.

What does the upper-left number in isotope notation represent?

Mass number.

What does the lower-left number in isotope notation represent?

Atomic number.

What does a superscript charge indicate?

The net charge of the atom or ion.

What is the difference between isotopes of an element?

They have different numbers of neutrons.

Do isotopes of an element have the same number of protons?

Yes; otherwise, they would be different elements.

What is average atomic mass?

The weighted average mass of an element's naturally occurring isotopes.

What is the atomic mass unit (amu or u)?

A unit used to express atomic and subatomic particle masses.

What is nuclear charge?

The total positive charge of the nucleus, equal to the number of protons times +1.

What is the elementary charge?

The magnitude of one proton's or electron's charge, about 1.602 × 10⁻¹⁹ coulombs.

What does charge magnitude mean?

The size of a charge without considering whether it is positive or negative.

How do a proton and electron compare in charge?

Equal charge magnitude but opposite signs.

How does electric force depend on charge magnitude?

It increases with the product of the charge magnitudes.

How does electric force depend on distance?

It decreases with the square of the distance between charges.

What is Coulomb's law?

F = k|q₁q₂|/r² for the magnitude of the electric force.

What happens to electric force if distance doubles?

The force becomes one-fourth as large.

What is an energy level or electron shell?

A main energy level that can contain electrons.

What is an orbital?

A region of space where an electron is likely to be found.

Do electrons follow fixed planetary paths around the nucleus?

No; modern models describe electron probability distributions, not fixed planetary paths.

How many electrons can the first shell hold?

2 electrons.

How many electrons can the second shell hold in the simplified model used in class?

8 electrons.

What is an electron configuration?

A representation of how an atom's electrons occupy energy levels or orbitals.

What is the ground state?

The arrangement in which electrons occupy the lowest available energy states.

What is the excited state?

A state in which one or more electrons occupy higher-energy states than in the ground state.

How does an atom become excited?

It absorbs energy, causing an electron to move to a higher-energy state.

What happens when an excited electron returns to a lower energy level?

The atom releases energy, often as a photon.

What does the Aufbau principle state?

Electrons fill lower-energy orbitals before higher-energy orbitals.

What is the shell configuration of an excited atom?

An arrangement with an electron promoted to a higher energy level than in the ground state.

How can you recognize an excited-state configuration?

An electron occupies a higher level while a lower level is not filled as it would be in the ground state.

What is electromagnetic radiation?

Energy that travels through space as oscillating electric and magnetic fields.

What is a wavelength?

The distance between corresponding points on consecutive waves.

What is frequency?

The number of wave cycles passing a point per second.

What is the unit of frequency?

Hertz (Hz), equivalent to s⁻¹.

What is the relationship between wavelength and frequency?

They are inversely proportional for electromagnetic radiation in a vacuum.

What is the speed of electromagnetic radiation in a vacuum?

Approximately 3.00 × 10⁸ m/s.

What equation relates wavelength, frequency, and wave speed?

c = λν.

What does λ represent?

Wavelength.

What does ν represent?

Frequency.

What does c represent in c = λν?

The speed of light in a vacuum.

How do you calculate frequency from wavelength?

ν = c/λ.

How do you calculate wavelength from frequency?

λ = c/ν.

What is the relationship between photon energy and frequency?

E = hν; energy increases as frequency increases.

What is Planck's constant?

h ≈ 6.626 × 10⁻³⁴ J·s.

How do you calculate photon energy from wavelength?

E = hc/λ.

How are wavelength and photon energy related?

They are inversely proportional.

Which has greater energy: red or violet light?

Violet light, because it has a higher frequency.

Which has a longer wavelength: red or violet light?

Red light.

What happens to frequency when wavelength increases?

Frequency decreases, assuming the wave travels at the same speed.

What happens to photon energy when frequency doubles?

Photon energy doubles.

What is the electromagnetic spectrum?

The full range of electromagnetic radiation arranged by wavelength or frequency.

What is a bright-line emission spectrum?

A set of discrete wavelengths emitted by excited atoms.

Why does each element have a unique line spectrum?

Each element has its own set of allowed electron energy levels.

How is a bright-line spectrum produced?

Excited electrons drop to lower energy levels and emit photons of specific energies.

Why do atoms emit only certain wavelengths?

Their electrons can change energy only by specific allowed amounts.

What does a line spectrum reveal about electron energies?

Electron energy levels are quantized.

What is a flame test?

A test that identifies certain metal ions by characteristic colors emitted when heated.

Why do different elements produce different flame colors?

Their electrons emit different photon energies as they return to lower levels.

What is the relationship between energy change and emitted photon energy?

Photon energy equals the energy difference between the initial and final electron states.

What did John Dalton propose?

Matter is made of atoms; atoms of each element differ from those of other elements, and compounds form in fixed ratios.

What atomic model is associated with Dalton?

The solid-sphere or billiard-ball model.

What was a limitation of Dalton's model?

It did not include subatomic particles or internal atomic structure.

What experiment is associated with J. J. Thomson?

Cathode-ray tube experiments.

What did Thomson discover?

The electron.

What did Thomson conclude from cathode-ray experiments?

Atoms contain negatively charged particles.

What atomic model is associated with Thomson?

The plum-pudding model, with electrons embedded in positive matter.

What was a limitation of Thomson's model?

It did not contain a small, dense nucleus.

What experiment is associated with Ernest Rutherford?

The gold-foil experiment.

What did Rutherford's gold-foil experiment involve?

Firing alpha particles at thin gold foil and observing their scattering.

What did most alpha particles do in Rutherford's experiment?

Pass straight through the foil.

What did the occasional large deflection of alpha particles show?

Positive charge and most atomic mass are concentrated in a small nucleus.

What did Rutherford conclude about atomic structure?

Atoms have a tiny, dense, positively charged nucleus and are mostly empty space.

What was a limitation of Rutherford's model?

It did not explain atomic stability or discrete line spectra.