Chemistry 20- Unit A

An ion is an atom or molecule with a net electrical charge.

• A positively charged ion that forms when an atom, usually a metal, loses one or more electrons.
• Ex: a sodium atom loses an electron, giving it a 1+ charge. It is now called a sodium ion.

• A negatively charged ion that forms when an atom, usually a nonmetal, gains one or more electrons.
• -If an atom is an anion-> change ending to -ide.
• Ex: a chlorine atom gains one electron, giving it a 1- charge. it is now called a chlorine ion.

Compounds made up of ions that form charged particles when an atom (or group of atoms) gains or loses electrons.

It forms when valence electrons transfer from one atom to another resulting in a formation of a cation(usually a metal) and an anion(usually a nonmetal). The cation and anion are attracted to one another by charge, forming a neutral ionic compound joined together by an ionic bond.

• A specific volume of space in which an electron of certain energy is likely to be found.
• -It may be unoccupied, contain one electron, or contain two electrons
• -The first energy level contains one orbital- hydrogen and helium have just one orbital
• -Energy levels above the first one contain four orbitals each

• The relative ability of an atom to attract a pair of bonding electrons.
• -Electronegativity decreases with an increased number of energy levels-> the further away from the nucleus, the weaker their attraction to the nucleus

Nonmetals tend to have high electronegativities.

States that chemical reactions involve the sharing or transfer of valence electrons so that each atom has a complete valence shell, or stable octet.

The simultaneous attraction of oppositely charged ions.

• It forms when there is an electronegativity difference between atoms is greater that 1.7, resulting in the complete transfer of one or more electrons from one atom to the other.
• -Since metals have lower electronegativity values and nonmetals have higher electronegativity values, ionic compounds are typically composed of a metal and a nonmetal.

Elements form compounds in order to complete their valence energy levels and become more stable- like the nearest noble gas.

Valence orbital that is occupied by a single electron.

Full valence orbital occupied by 2 electrons.

• Ions arrange themselves in a crystal lattice where the maximum total attraction between cations and anions occur.
• -Non-directional

Hard, brittle, high melting and boiling point, liquid and solution are electrolytic, soluble in water, and relatively stable and unreactive at SATP

Ionic bonds are strong and difficult to break.

Ions cannot be rearranged without breaking the crystal lattice structure.

Ionic bonds require large amounts of energy to break.

It is due to the presence of moving charges.

It is due to the attraction between ions and partially negative and partially positive end of the polar water molecules.

It is because valence shells are full.

An independent unit made up of fixed numbers of nonmetallic atoms held together by covalent bonds.

Don't exist naturally as single atoms; they consist of two or more nonmetallic atoms of the same element joined by a covalent bond.

Composed of two atoms of the same element joined together by a covalent bond. The diatomic elements are hydrogen(H₂), nitrogen(N₂), oxygen(O₂), fluorine(F₂), chlorine(Cl₂), bromine(Br₂), and iodine(I₂).

Composed of many atoms of the same element joined by covalent bond. The polyatomic elements are phosphorus(P₄), sulfur(S₈), and ozone(O₃).

Composed of two or more nonmetallic atoms of different elements joined by covalent bonds.

The simultaneous attraction of two nuclei for a shared pair of bonding electrons forming a strong, directional intramolecular force.

Forms so atoms can complete their valence shells. Occurs when electronegativities of both atoms, usually nonmetals, are relatively high.

• The maximum number of single covalent bonds that an atoms can form.
• -Determined by the number of bonding electrons

States that pairs of electrons in the valence shell of an atom stay as far apart as possible because of the repulsion of their negative charges.

• When there is symmetrical electron charge distribution among atoms.
• -Forms when the atoms have an electronegativity difference of 0.4 or less

• When electrons spend more time closer to one atomic nucleus than the other, resulting in a partial positive end and a partial negative end.
• -Forms when the atoms have an electronegativity difference greater than 0.4 but less than 1.7
• -The greater the electronegativity difference, the more polar the bond

• All chemical bonding involves the movement of electrons between atoms so that each atom can achieve a stable octet.
• -Chemical bonding may be viewed as a continuum ranging from equal sharing of electrons to complete electron transfer

• The forces of attraction and repulsion between molecules.
• -Intermolecular forces are weaker than covalent bonds
• -Exists between molecules

• The forces that hold atoms together within a molecule.
• -Covalent bonds are intramolecular

• The attraction between permanent dipoles in adjacent polar molecules.
• -The more polar the molecule, the stronger the dipole-dipole force

• From momentary, or induced, dipoles due to electron movement within molecules.
• -Occurs in all substances

When a hydrogen atom is bonded to a strongly electronegative atom with a lone pair of electrons- F,O, or N.

The highly electronegative atom pulls the electrons away from the hydrogen, resulting in attraction between the lone pair and the unshielded hydrogen proton on an adjacent molecule.