Chemistry Periodic Trends Flashcards
specific patterns in the periodic table that make it possible to make predictions about an element’s properties
periodic trends
as the atomic number increases, the nuclear attraction for electrons increases, thus pulling the electrons in more tightly to the nucleus
Coulomb’s law
one-half the distance between the nuclei of two identical atoms bonded together
atomic radius
a measure of how readily an atom will react
reactivity
when electrons in the inner energy levels block the attraction of the nucleus to the valence electrons
shielding effect
a measure of the ability of an atom in a bond to attract electrons
electronegativity
the energy required to remove one electron from a neutral atom of an element
ionization energy
the charge of an ion
oxidation numbers
the radius of a monoatomic ion in an ionic compound
ionic radius
Summarize the connection between Coulomb’s law and the periodic trends.
This law explains why we see the trends we see in atomic radii, reactivity, electronegativity, etc. It is all about how tightly the electrons are being held to the nucleus, which is impacted by the number of protons in the nucleus, and the number of electrons both the total and specifically in the outermost energy level.
Explain the following trends seen in the periodic table. Use a visual if it helps you explain the patters. Ionic radii:
Atoms that lose electrons become smaller
Atoms that gain electrons become larger
Tends to increase as you go DOWN a group
Explain how the shielding effect works.
This occurs when electrons in the inner energy levels block the attraction of the nucleus to the valence electrons, and thus they become more loosely held.
Describe how the difference in electronegativity between two atoms can be used to predict the type of bond that could form. Include an example to support your description.
EN shows if one atom will more strongly attract the electrons than the other. If the attraction is super strong (EN > 2), an ionic bond forms because one takes the electrons from the other. If the attraction is very low (EN < 0.5), a covalent bond forms and the electrons are mostly equally shared. If EN is somewhere in the middle, a polar covalent bond is formed where electrons are unequally shared.
Ex. Atmospheric nitrogen (N2) makes an EN = 0, thus a covalent bond will form and electrons will be equally shared.
Identify the oxidation numbers for elements in groups 1, 2, and 13-17.
Group 1 - +1
Group 2 - +2
Group 13 - +3
Group 14 - +/-4
Group 15 - -3
Group 16 - -2
Group 17 - -1
Be able to make distinctions between elements using the periodic trends when given a model, description, or example.
Be able to make predictions about how main group elements will behave based on their location on the periodic table.
Be able to calculate the difference in electronegativity between two atoms and use it to predict the type of bond that would form.
Be able to identify a cation or anion based on a picture, description, or example.
Explain atomic radius:
the atomic radius can be determined by measuring the distance between two adjoining nuclei in a molecule comprised of two identical atoms, and then dividing two.
For nonmetallic atoms that do not form diatomic molecules, the radius is determined by measuring the radius of atoms in covalent compounds.
For metallic atoms, the radius is determined by measuring the radius of atoms in metallic crystals.
The Periodic Trends Gizmo uses calculated atomic radii established by Enrico Clementi and others in 1967.
Explain Ionization Energy:
ionization energy refers to an atom’s tendency to hold on to its electrons.
the lower an atom’s ionization energy, the more likely that atom is to lose electrons
he first ionization energy is the energy needed to remove a single valence electron from an atom, the second ionization energy is the energy required to remove an additional valence electron, etc. ionization energy increases with the removal of each successive electron
Explain Electron Affinity:
electron affinity refers to the tendency of an atom to attract electrons.
an element with a strong attraction for electrons will have a high negative electron affinity, since energy is released when an electron is added. the greater the magnitude of the negative electron affinity value, the stronger the attraction for electrons
Explain electron cloud:
the electron cloud can be considered a probability distribution representing the space where electrons are most likely to be found
Explain energy level:
the number of principal energy levels within an atom is equal to that atom’s period number on the periodic table.
there are a maximum of 7 principal energy levels within an atom
explain a group:
groups are also called families.
elements in the same group have the same number of valence electrons and similar chemical properties
explain an ion
an atom with more protons than electrons is a positively charged ion, or cation
an atom with more electrons than protons is a negatively charged ion, or anion
in an element symbol, the electric charge is a shown as a superscript at the upper right. For example, Be2+ is an ion of beryllium with a charge of positive 2
explain metal
metal atoms tend to hold electrons loosely
metal atoms tend to lose electrons, forming positive ions
metals typically have a low ionization energy and a low electron affinity
explain nonmetal
nonmetal atoms tend to hold electrons tightly
nonmetal atoms tend to gain electrons, forming negative ions
nonmetals typically have a high ionization energy and a high electron affinity
explain nucleus
the total number of particles (protons and neutrons) in the nucleus is given by the atom’s mass number
the nucleus contains over 99.9% of an atom’s mass, but onlu occupies about 1/100,000 of its volume
explain period
elements within the same period share the same number of principal energy levels
unit of length used to measure atomic radius that is equal to one-trillionth (10^-12) of a meter
picometer
an electron found in the outermost energy level of an atom
valence electron
