Chemistry Unit Test

Valance Electrons

1. Electrons found in the outermost energy levels, farthest from the nucleus 2.They are involved in chemical bonding Valence electrons are those occupying the outermost shell or highest energy level of an atom while core electrons are those occupying the innermost shell or lowest energy level.

Electronegativity trend

From left to right across a period of elements, electronegativity increases. If the valence shell of an atom is less than half full, it requires less energy to lose an electron than to gain one. Conversely, if the valence shell is more than half full, it is easier to pull an electron into the valence shell than to donate one. From top to bottom down a group, electronegativity decreases. This is because atomic number increases down a group, and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius

Valence Electrons trend

In a period, the number of valence electrons increases (mostly for light metal/elements) as we move from left to right side. In a group this periodic trend is constant, tht is the number of valence electrons remains the same.

Energy Level

Inside an atom are the specific energies that electrons can have when occupying specific orbitals. Electrons can be excited to higher energy levels by absorbing energy from the surroundings.

Family

Is a column of elements on the periodic table. Each member of a family has the same number of valence electrons. Family members share similar chemical and physical properties. An element family is also called an element group.

Ground State electron Configuration

Is the arrangement of electrons around the nucleus of an atom with lower energy levels. The electrons occupying the orbitals of varying energy levels naturally falls towards the lowest energy state or ground state. Is an atom in which the total energy of the electrons can not be lowered by transferring one or more electrons to different orbitals. All electrons are in the lowest possible energy levels.

Coulombic Attraction

Is the attraction between oppositely charged particles. For example, the protons in the nucleus of an atom have attraction for the electrons surrounding the nucleus. The positive charge of the proton and the negative charge of an electron create an electrostatic force of attraction between the atom's nucleus and its electrons. This force of attraction is also known as coulombic attraction. Two variables affect the strength of this attraction: The distance between the charged particles The force of attraction has an indirect relationship with the square of the distance. This means that as the distance between the nucleus and the electron increases the electrostatic attraction decreases. Because the relationship is with the square of distance the force decreases rapidly as the distance increases. The strength of the charged particles The force of attraction has a direct relationship with the strength of the charged particles. An electron can only have a 1- charge; however, the strength of the nucleus charge is equal to the number of protons in the nucleus. So as the number of protons in the nucleus increases the strength of the electrostatic attraction between the nucleus and the electron increases.

Ionization Energy

Is the energy required to remove an electron from a neutral atom in its gaseous phase. It is the opposite of electronegativity. The lower this energy is, the more readily the atom becomes a cation. Therefore, the higher this energy is, the more unlikely it is the atom becomes a cation. Generally, elements on the right side of the periodic table have a higher ionization energy because their valence shell is nearly filled. Elements on the left side of the periodic table have low ionization energies because of their willingness to lose electrons and become cations. Thus, ionization energy increases from left to right on the periodic table.

Excited State Electron configuration

Means that (typically) the valence electron has moved from its ground state orbital ( lowest available energy) to some other higher energy orbital.

ionization energy trend

The ionization energy of the elements within a group decreases from top to bottom. This is due to electron shielding. The noble gases possess very high ionization energies because of their full valence shells. Note that helium has the highest ionization energy of all the elements. As you go down the group, the atomic radius increases, the ionization energy decreases, the ionization energy decreases. This is because the force force btw the electron and the nucleus decreases, requiring less energy to take the electron. AS you across the period, the atomic radius decreases making the force of attraction increase (more energy being used when it is takes away)

Sublevel

The levels can be broken down into sublevels. We have s, p, d, and f sublevels. Level one has one sublevel - an s. Level 2 has 2 sublevels - s and p. Level 3 has 3 sublevels - s, p, and d. Level 4 has 4 sublevels - s, p, d, and f.

Atomic Radius

The size of the atom The atomic radius is one-half the distance between the nuclei of two atoms (just like a radius is half the diameter of a circle) Atomic size gradually decreases from left to right across a period of elements. This is because, within a period or family of elements, all electrons are added to the same shell. However, at the same time, protons are being added to the nucleus, making it more positively charged. The effect of increasing proton number is greater than that of the increasing electron number; therefore, there is a greater nuclear attraction. This means that the nucleus attracts the electrons more strongly, pulling the atom's shell closer to the nucleus. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases.

Orbital

The sublevels contain orbitals. Orbitals are spaces that have a high probability of containing an electron. In other words, an orbital is an area where the electrons live.

Orbital diagram

a visual representation of where the electrons are in an atom. we're going to include energy levels sublevels and orbitals in this representation

Groups

a. Also called families or columns b. Run vertically on the table c. Elements in the same group have similar properties - including the same # of valence electrons. There are 18 groups

Period

horizontal rows (across) the periodic table

Electronegativity

measures an atom's tendency to attract and form bonds with electrons. For example: The chlorine atom has a higher electronegativity than the hydrogen atom, so the bonding electrons will be closer to the Cl than to the H in the HCl molecule.