CHEMISTRY FOR ENGINEERS MIDTERM EXAMS Flashcards
substances that assume regular, repeating patterns of arrangement of their atoms. substances condense into crystals as solids that fill space as completely as possible.
crystals
can be thought of as spheres, and how they fill up a theoretical cubical box called a unit cell.
atoms
the seven crystal structures
simple cubic, face-centered cubic, body-centered cubic, hexagonal closed pack, orthorhombic, rhombohedral, tetragonal, and monoclinic
made up of atoms at each corner of a cube, and is envisioned as eight spheres on eight corners of a cube. this structure has equal sides, with all the angles of each side as 90.
this is a rare structure and the only elements that occur in this structure are oxygen, fluorine and polonium.
simple cubic
crystal system is more common. it is made up of atoms at each corner of a cube with atoms on each “face”
many elements occur as this crystal system in their solid states like aluminum, silver, copper, gold, and nickel. gases in family 8A.
face-centered cubic
made up of atoms at each corner of a cube but has an atom at the center.
the alkali metals in group 1A and barium and radium from group IIA are some of the elements
body-centered cubic
atoms are piled as layers of hexagons with one atom on each corner and a center atom on the hexagon. the next layer of atoms fill the spaces in between the atoms of the first layer, hence, closed packed.
titanium, zinc, magnesium, and cadmium, including helium and hydrogen gases.
Hexagonal closed packed
orthorhombic crystals or rhombic system
consists of three equal angles of 90 degrees. the sides are of different lengths. four types of unit cells, primitive, face-centered, body-centered, and side centered.
sulphur, chlorine, bromine, iodine, protactinium, and neptunium.
its axes (a, b, c) are all equal. its corner angles are equal, and all are not perpendicular.
mercury, antimony, and bismuth
rhombohedral or trigonal system
three corner angles are perpendicular and two of its sides are of equal length, with the third side either longer or shorter than the other two.
indium and tin
tetragonal
three unequal sides comprise it. sides a and c are inclined toward each other at an oblique angle, while the third side b is perpendicular to a and c. two angles are perpendicular while the third angle is not.
curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium
monoclinic
elements that generally are that are shiny, good conductors of heat and electricity, ductile and malleable. they have the ability to conduct heat and electricity due to the closely packed arrangement of their atoms, making it easier for each atom to transfer with each other.
metals
property of metals to be pulled into wires, while malleability is the property of metals to be formed into sheets. it is because of these properties that metals and their alloys can be formed into different shapes such as pipes, tubes, or bars.
ductility
the row in a periodic table, elements in the same period are same in size.
period (or series)
the column in a periodic table, elements in the same group have the same chemical and electronic properties
group (or family)
elements in families IA to 7A.
representative elements
these have complete fills s and p subshells
noble elements (group 8A or O)
elements in 1B to (B they have filled d orbitals
transition metals
elements with no group numbers and have filled f orbitals
inner transition metals.
determined by the atomic radius (distance of the valence shell from the nucleus)
atomic size
it measures the willingness of an atom to receive electrons, ability of an atom to attract a bonding electron towards itself
electronegativity.
an ion with a positive charge. if a neutral atom loses one or more electrons, it becomes this.
cation
an ion with a negative charge. if a neutral atom gains one or more electrons, it becomes this
anion
is defined as the tensile force per unit area, hence represented by the formula o=F/A
tensile stress
refers to change in length per original length, hence represented by the formula e=^L/Lo
tensile strain
ratio of stress to strain. it is represented by the formulas:
1) Y=FLo/A^L and
2) Y = o/e
young’s modulus of elasticity
refers to the ratio of the change in magnitude of the applied force to the surface area. it is the force per unit area that causes deformation.
Formula: ^P = ^F/A
Bulk stress
defined as the ratio of the change in volume, either by compression or expansion, to the original volume. it is the fractional decrease (or increase) in volume.
Formula: e= ^V/ Vo
Bulk strain
is defined as the ratio of the applied force per unit area
formula: P= F/A
Pressure
refers to the increase in volume of a body due to changes in temperature or decrease in pressure.
expansion
refers to the decrease in volume of a body due to compressive force or increase in pressure.
compression.
is defined as the resistance of a solid or liquid to a change in volume.
Formulas:
^F/A = -B ^V/Vo
(By substituting ^P)
^P= -B^V/Vo
Bulk Modulus
