CHEM100 Concept Flashcards

What is Hund's Rule?

Electrons fill orbitals singly before pairing and have parallel spins.

How do you draw an orbital diagram using Hund's Rule?

Place one electron in each orbital before pairing electrons.

What are core electrons?

Inner-shell electrons that do not participate in bonding.

What are valence electrons?

Electrons in the outermost energy level that participate in bonding.

Which electrons are at the highest energy level?

Valence electrons in the outermost shell.

How do you determine the number of valence electrons using the periodic table?

Use the group number for main group elements.

How do you determine the number of core electrons?

Subtract valence electrons from the total number of electrons (atomic number).

What is a chemical bond?

A force that holds atoms together by sharing or transferring electrons.

What are the two main types of chemical bonds?

Ionic bonds and covalent bonds.

Which type of bond involves transfer of electrons?

Ionic bonds.

Which type of bond involves sharing electrons?

Covalent bonds.

What types of elements form ionic bonds?

Metals and nonmetals.

What types of elements form covalent bonds?

Two nonmetals.

How do ionic and covalent compounds differ in properties?

Ionic compounds typically have higher melting and boiling points and form solid crystals, while covalent compounds are often gases, liquids, or softer solids.

What is the Octet Rule?

Atoms tend to gain, lose, or share electrons to achieve 8 valence electrons.

What is the Duet Rule?

Hydrogen becomes stable with 2 electrons.

How do you draw a Lewis dot structure?

Count total valence electrons, choose the central atom, connect atoms with single bonds, distribute remaining electrons as lone pairs, and form double or triple bonds if needed.

How do you determine the central atom in a Lewis structure?

Usually the least electronegative atom except hydrogen.

What are lone pairs?

Pairs of valence electrons not involved in bonding.

What are bonding pairs?

Pairs of electrons shared between atoms in a bond.

What is VSEPR Theory?

Valence Shell Electron Pair Repulsion theory states that electron groups repel each other and arrange as far apart as possible.

How do lone pairs affect molecular shape?

They repel more strongly and reduce bond angles.

How does the number of atoms bonded to the central atom affect shape?

It determines the molecular geometry based on electron group arrangement.

What are the three parent structures in VSEPR?

Linear, trigonal planar, tetrahedral.

What is the bond angle of linear molecules?

180°.

What is the bond angle of trigonal planar molecules?

120°.

What is the bond angle of tetrahedral molecules?

109.5°.

How do you determine molecular shape from a Lewis structure?

Count the number of electron groups around the central atom and apply VSEPR geometry rules.

How do you draw a Lewis structure for a polyatomic ion?

Count valence electrons, draw the structure, place brackets around it, and write the charge outside the brackets.

What is polarity in bonds?

Unequal sharing of electrons in a bond.

What is electronegativity?

The ability of an atom to attract electrons in a chemical bond.

How does electronegativity relate to bond polarity?

A greater electronegativity difference creates a more polar bond.

What is a dipole moment?

A vector arrow showing the direction of electron pull toward the more electronegative atom.

How do you determine if a molecule is polar?

Determine if bonds are polar and whether the molecular shape cancels or reinforces dipoles.

What are intermolecular forces?

Attractive forces between molecules.

What are the three types of intermolecular forces?

Dispersion forces, dipole-dipole forces, hydrogen bonding.

What are dispersion forces?

Weak attractions caused by temporary electron movement creating temporary dipoles.

What types of molecules have dispersion forces?

All atoms and molecules.

How does molecular size affect dispersion forces?

Larger atoms and molecules have stronger dispersion forces.

What are dipole-dipole forces?

Attractions between polar molecules.

What is hydrogen bonding?

Strong dipole interaction when hydrogen is bonded to nitrogen, oxygen, or fluorine.

How do you identify hydrogen bonding in a molecule?

Look for hydrogen bonded directly to N, O, or F.

How do you draw hydrogen bonding between molecules?

Show hydrogen from one molecule interacting with a lone pair on N, O, or F of another molecule.

How do intermolecular forces affect boiling point?

Stronger intermolecular forces increase boiling point.

What is an ionic bond?

Attraction between oppositely charged ions formed by electron transfer.

How do metals and nonmetals form ions?

Metals lose electrons to form cations and nonmetals gain electrons to form anions.

What is a monatomic ion?

An ion formed from a single atom.

What is a polyatomic ion?

A group of atoms with an overall charge.

How do you determine charges of main group ions?

Use their periodic table group.

Which metals commonly have multiple charges?

Most transition metals plus lead and tin.

What are metals with fixed charges?

Silver +1, zinc +2, cadmium +2.

How do you write the formula of an ionic compound?

Balance the positive and negative charges so the total charge equals zero.

What is the atomic radius trend across the periodic table?

Decreases from left to right.

What is the atomic radius trend down a group?

Increases down the periodic table.

What is effective nuclear charge?

The net positive charge experienced by valence electrons.

How does ionic size compare to neutral atoms?

Cations are smaller and anions are larger.

What is ionization energy?

Energy required to remove an electron from an atom.

What is the ionization energy trend across the periodic table?

Increases from left to right.

What is the ionization energy trend vertically?

Increases upward.

What is the electronegativity trend across the periodic table?

Increases left to right.

What is the electronegativity trend vertically?

Increases upward.

What is the most electronegative element?

Fluorine.

How do you name ionic compounds?

Write the metal name followed by the nonmetal ending in -ide.

When are Roman numerals used in naming?

When a metal can have multiple charges.

How do you name molecular compounds?

Use prefixes to indicate the number of atoms.

What are common prefixes used in naming molecular compounds?

mono, di, tri, tetra, penta, hexa, hepta, octa.

What is scientific notation?

Writing numbers as a coefficient multiplied by a power of 10.

How do you convert a number to scientific notation?

Move the decimal until one nonzero digit remains on the left and count the number of places moved.

Why are significant figures used in science?

To represent measurement precision.

What is accuracy in measurements?

How close a measurement is to the true value.

What is precision in measurements?

How close repeated measurements are to each other.

What is the significant figure rule?

Nonzero digits are significant, zeros between numbers are significant, leading zeros are not significant, and trailing zeros after decimals are significant.