Chemistry Chapter 5: Emission Spectra and Isotopes

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Questions and Answers

What determines the distinct colors visible in emission spectra for elements?

Different isotopes of the element

Variations in temperature during excitation

Consistent photon frequency due to energy level transitions (correct)

Random placement of electrons in energy levels

Which of the following describes the correct filling order of electrons for the first 20 elements?

2, 8, 8, 2, 2

2, 8, 10, 2

2, 6, 8, 4

2, 8, 8, 2 (correct)

Isotopes of an element differ in which of the following subatomic particles?

Protons

Electrons

Neutrons (correct)

Photons

When drawing a Bohr-Rutherford diagram for an isotope, what is crucial to know?

The specific isotope being represented Signup and view all the answers

What role do quantum models play in the behavior of electrons during excitation?

They explain the energy level transitions and subshell configurations Signup and view all the answers

Why is the mass of 28Si less than 28?

Atoms in a more energetic state have mass due to energy. Signup and view all the answers

What tool is commonly used to determine the isotopic abundance of a sample?

Mass spectrometer Signup and view all the answers

How would you calculate the average donation from 10 friends giving $20 and 2 friends giving $10?

Average donation = (10 x $20 + 2 x $10) / 12 Signup and view all the answers

Which equation correctly represents the relative atomic mass (Ar) calculation?

Ar = (% abundance of isotope 1 x mass of isotope 1) + (% abundance of isotope 2 x mass of isotope 2) Signup and view all the answers

What is the average atomic mass indicative of in terms of isotopes?

It represents a weighted average based on isotope abundance. Signup and view all the answers

What occurs when an ionic compound is dissolved in water?

It conducts electricity. Signup and view all the answers

Which of the following correctly describes the naming convention for ionic compounds?

Name of metal + name of nonmetal with -ide suffix Signup and view all the answers

What is the correct way to indicate a multivalent metal ion in a compound's name?

Adding a Roman numeral to specify its charge Signup and view all the answers

What is an example of a formula that includes a polyatomic ion?

Ca(OH)2 Signup and view all the answers

Which of the following elements exists as a diatomic molecule?

Nitrogen (N2) Signup and view all the answers

What is the definition of ionization energy?

The energy required to remove a single valence electron from an atom in the gaseous state. Signup and view all the answers

What happens to ionic compounds when a force is applied?

They shatter due to ionic interactions. Signup and view all the answers

How is electron affinity defined?

The energy released when an atom gains an electron in the gaseous state. Signup and view all the answers

What is the subscript that must be used for diatomic elements when they are alone?

2 Signup and view all the answers

What does electronegativity indicate about an atom?

How strongly an element will attract electrons in a bond. Signup and view all the answers

What defines a molecular element?

Two atoms of the same element bonded together. Signup and view all the answers

Which statement accurately describes ionic compounds?

They are represented by the ratio of ions in a simplified formula unit. Signup and view all the answers

What characteristic property do ionic compounds exhibit?

High melting and boiling points due to strong ionic bonds. Signup and view all the answers

Why do ionic compounds form a crystal lattice structure?

To reduce energy by maximizing attractive forces between ions. Signup and view all the answers

In a bond where electrons are completely taken to one side, what type of bond is formed?

Ionic bond Signup and view all the answers

How are molecular compounds different from ionic compounds in their chemical formula representation?

They must show every atom in the molecule in the formula. Signup and view all the answers

What defines the bond character between ionic, polar covalent, and nonpolar covalent?

The electronegativity difference Signup and view all the answers

If a bond has an electronegativity difference of 1.5, what type of bond is it likely to be?

Polar covalent bond Signup and view all the answers

Why can a molecule with polar bonds still be nonpolar overall?

If the molecular shape allows bond dipoles to cancel out Signup and view all the answers

Which molecule is likely to have a net dipole moment due to its shape?

Water Signup and view all the answers

What is true regarding the C=O bond in a linear molecule?

The bond dipoles cancel each other out Signup and view all the answers

In a molecule like methane, what characterizes its nonpolarity?

Symmetrical arrangement of bonds Signup and view all the answers

What property does the lowercase Greek letter delta (+/-) signify in a bond?

It represents partial charges Signup and view all the answers

Which of the following molecules is more likely to have polar character?

Methanol Signup and view all the answers

Study Notes

Emission Spectra

Different colours are visible when elements are excited.
These colours are consistent for that element because electrons are moving between energy levels.
This involves the same amount of energy each time, resulting in the same photon frequency.
Electrons don't fill energy levels perfectly level by level.

Isotopes

Isotopes are different versions of the same element.
Isotopes have the same number of protons but a different number of neutrons.
For B-R diagrams, you should know which isotope you're working with.
Atoms in a more energetic state (less stable) have some of their energy in the form of mass, and vice versa.
Atomic mass can be less than the sum of protons and neutrons due to this energy-mass relationship.
Isotopic abundance can be determined using a mass spectrometer.

Determining Atomic Mass of Elements

The average donation analogy helps understand how to calculate atomic mass of an element.
The relative atomic mass (Ar) is calculated by multiplying the percentage abundance of each isotope by its mass, adding those numbers, and dividing by 100.

First Ionization Energy

The amount of energy needed to remove one valence electron from an atom or ion in a gaseous state.

Electron Affinity

The energy change that occurs when an atom in the gaseous state gains an electron.
Electron affinity follows a similar trend to ionization energy.

Electronegativity

How strongly an element attracts electrons within a chemical bond.
Big electronegativity differences lead to ionic bonds, while smaller differences lead to covalent bonds.
Electronegativity determines the sharing of electrons in a bond, which can be even, uneven, or complete transfer.

Structure of Ionic Compounds

Ionic compounds have a crystal lattice structure.
Ionic compounds are represented by the ratio of ions, not individual atoms.
Formulas are simplified to reflect the lowest whole-number ratio, for example, MgO.
Ionic compounds have high melting and boiling points because of the strong ionic attraction.
Ionic compounds are often soluble in water because the polar water molecules can break apart the lattice through attraction.
Dissolved ionic compounds conduct electricity because the separated ions can move and carry current.
Ionic compounds are hard and brittle because applying force can shift the lattice and cause repulsive forces between ions.

Naming Ionic Compounds

Use the name of the metal followed by the name of the nonmetal with an "-ide" suffix. For example, NaCl is sodium chloride.
The formula unit ratio doesn’t influence the name.
Multivalent metals require roman numerals to indicate their charge. For example, copper(I) chloride or copper(II) chloride.

Polyatomic Ions

Polyatomic ions are groups of atoms covalently bonded together with an overall charge.
Enclose multiple polyatomic ions in brackets in the formula unit. For example, Ca(OH)2.

Molecular Elements

Diatomic elements are elements that exist as pairs of atoms covalently bonded together.
HOFBrINCl: Diatomic elements, like hydrogen, oxygen, bromine, fluorine, iodine, nitrogen, and chlorine.
Diatomic elements form when on their own to complete the valence level.
These can be single, double, or triple covalent bonds.

Covalent Bonding

Covalent bonding occurs when two atoms share electrons.
Both atoms achieve a stable electron configuration similar to a noble gas.
The bond character (ionic, polar covalent, or nonpolar covalent) depends on the electronegativity difference between the atoms.
Electronegativity difference between 0 - 2.0 (ish) indicates a polar covalent bond.
Polar covalent bonds have a bond dipole, with a negative side and a positive side.

Molecular Polarity

Just because a molecule has a polar bond does not necessarily mean the entire molecule is polar.
A molecule needs a “net dipole moment” for it to be polar.
This means that the individual bond dipoles don’t cancel each other out completely.
Water is a polar molecule because its bent shape and uneven sharing of electrons create a net dipole moment.

Water vs. Methane/Methanol

Methane and ethanol are both organic compounds with one carbon atom.
Methane is non-polar due to its tetrahedral shape and balanced bond dipoles.
Methanol is polar due to the oxygen atom’s attraction for electrons, creating a net dipole moment in the molecule.
This dipole moment makes methanol more likely to bend due to the partial negative charge on the oxygen atom.

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Description

Explore the fascinating concepts of emission spectra, isotopes, and atomic mass in this quiz. Discover how electrons transition between energy levels to produce unique colors for each element and learn about the properties of isotopes and their significance in atomic mass calculations. Test your knowledge on these fundamental topics in chemistry!