Atoms properties

Properties OF ATOMS

ELECTRONEGATIVITY

COMPOUNDS AND COVALENT BONDS

CRYSTAL STRUCTURES

BOILING AND MELTING POINTS

IONISATION ENERGY

IONIC BONDS

Atoms have different properties that make them act differently in different situations.Here you can find explanation of what each of those properties mean for the atoms

ELECTRONEGATIVITY

Electronegativity is the tendency of an atom to attract the electrons of a chemical bond.- Two atoms with the same value of electronegativity share electrons equally in a covalent bond.- When the electronegativity of the atoms is different, the electrons of the bond are attracted to the most electronegative atom. This results in a polar covalent bond. - If the atoms of a bond have very different electronegativity, the electrons aren't shared at all. The most electronegative atome takes the bond electrons from the other atom, forming an ionic bond.Atoms that have a nuclei that exerts a strong pull on electrons have high electronegativity (and high ionization energy). To the contrary, atoms that have low electronegativity (and low ionization energy) have a nuclei that does not exert a strong pull on electrons.As ionization energy, in the periodic table, electronegativity generaly increase moving rightward along a period and upward along a group. Noble gases tend to be exception to this trend.

HOME

Illustration found in the textbook: The Cartoon Guide to Chemistry

A compound is en entity composed of several atoms. Binary compounds are compounds made up two elements.A covalent bond is a chemical link between two atoms or ions in which 2 electrons are shared: each atom brings one electron to share. They form between two nonmetal atoms with identical or relatively close electronegativity values.Two important types of covalent bonds exist:- nonpolar or pure covalent bonds: they occur when atoms equally share the electron pair. The electronegativity difference between the two atoms is less than 0.4.- polar covalent bonds: they occur when the electronegativity between the two atoms increase (a difference between 0.4 and 1.7)When the electronegativity difference is more than 1.7, the most electronegative atom takes the pair of electron and the bond becomes an ionic bond.

HOME

COMPOUNDS AND COVALENT BONDS

Illustration found in the textbook: The Cartoon Guide to Chemistry

Solids exists in two different forms according to the organization of their particules. - amorphous: a solid has an amorphous structure when its particules are posittioned in no particule pattern- crystalline: in a crystalline structure, atoms, molecules, or ions are perfectly organised according to a specific pattern

HOME

CRYSTAL STRUCTURES

A crystal structure is the arragement of atoms, ions, or molecules in a cristalline solid. The cristal structures are described in terms of crystal's geometric form and the spots where the atoms, ions, or molecules are.There are 7 crystal system (form of crystal): cubic, monoclinic, orthorombic, rhombohedral, tetragonal, hexagonal, and triclinic.There are 4 different types of placements for the particules: simple, face-centered, body-centered, and end face-centered.The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage, electronic band structure, and optical transparency.

The melting point of a substance is the temperature at which a solid and liquid phase may coexist in equilibrium and the temperature at which matter changes from solid to liquid form. The term applies to pure liquids and solutions. Melting point depends on pressure, so it should be specified. Typically, tables of melting points are for standard pressure, such as 100 kPa or 1 atmosphere. Melting point may also be called the liquefaction point.The temperature at which a liquid changes to a solid (the reverse of melting) is the freezing point or crystallization point. The freezing point and the melting point do not necessarily occur at the same temperature.

HOME

Definitions: thoughtco.comIllustrations found in the textbook: The Cartoon Guide to Chemistry

MELTING POINT

BOILING POINT

The boiling point is the temperature at which the vapor pressure of a liquid equals the external pressure surrounding the liquid. Therefore, the boiling point of a liquid depends on atmospheric pressure. The boiling point becomes lower as the external pressure is reduced. As an example, at sea level the boiling point of water is 100 C (212 F), but at 6,600 feet the boiling point is 93.4 C (200.1 F).Boiling differs from evaporation. Evaporation is a surface phenomenon that occurs at any temperature in which molecules at the liquid edge escape as vapor because there is not enough liquid pressure on all sides to hold them. In contrast, boiling affects all molecules in the liquid, not just those on the surface. Because molecules within the liquid change to vapor, bubbles form.

Ionic bonds occure when the two atoms bonding have a high difference in their electronegativity value.The most electronegative atom takes the electron of the least electonegative one and both become ions. The atom taking the electrons becomes an anion (negatively charged ion) and the one giving up its electrons becomes a cation (positively charged ion).An ionic bond is actually the extreme case of a polar covalent bond, the latter resulting from unequal sharing of electrons rather than complete electron transfer. Ionic bonds typically form when the difference in the electronegativities of the two atoms is great (more than 1.7), while covalent bonds form when the electronegativities are similar.Since both atoms are now oppositely-charged ions, a chemical link caused by the electrostatic force appear between them: it's the ionic bond.There is an ionic bond between the sodium and chloride ions in table salt, NaCl.

HOME

IONIC BONDS

Illustration found in the textbook: The Cartoon Guide to Chemistry

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. The first or initial ionization energy or Ei of an atom or molecule is the energy required to remove one mole of electrons from one mole of isolated gaseous atoms or ions.You may think of ionization energy as a measure of the difficulty of removing electron or the strength by which an electron is bound. The higher the ionization energy, the more difficult it is to remove an electron. Therefore, ionization energy is in indicator of reactivity. Ionization energy is important because it can be used to help predict the strength of chemical bonds.It is reported in units of kilojoule per mole (kJ/mol) or electron volts (eV).Ionization, together with atomic and ionic radius, electronegativity, electron affinity, and metallicity, follows a trend on the periodic table of elements: it increases moving rightward along a period and upward along a group.

HOME

IONIZATION ENERGY

Definitions: thoughtco.comIllustrations found in the textbook: The Cartoon Guide to Chemistry