Chemistry-midterm 2022-2023
Define Chemistry
The study of matter and the changes it undergoes
If a theory is accepted for a long time, it becomes a
Law
Your conclusions should be based on what info?
The data collected during an investigation
Is density Chemical or Physical
Physical
is color chemical or physical
physical
List the three states of matter and the differences between them
solid, liquid, and gas. Solids have a definite shape and volume. Liquids have a definite volume, but take the shape of the container. Gases have no definite shape or volume.
Explain the law of conservation of mass
mass that is neither created nor destroyed
Explain the law of definite proportions
a conpound is always composed of the same elements in the same elements in the same proportions by mass, no matter how large or small the sample
Homogeneous mixture
Constant composition
homogeneous ex
oxygen
Heterogeneous
mixture that does not blend smoothly
heterogeneous ex
blood
What is an element?
Substance that can no longer be broken down further
What is the definition of an atom?
Smallest particle of an element that retains the properties of an element
what is electrons symbol, location, and charge?
Negative charge, e-, outside the nucleus
what is protons symbol, location, and charge?
Positive charge, p+, in the nucleus of the atom
what is neutrons symbol, location, and charge?
Neutral charge, n0, inside the nucleus of every atom
how do you determine the number of neutrons in an atom?
atomic # - atomic mass
All atoms of any given element have the same number of
protons
explain the aufbau principle
electrons fill lower - energy atomic orbitals
before filling higher - energy ones
explain the pauli exclusion principle
no 2 electrons in the same atom can have identical values for all 4 of their quantum numbers
Explain the Hund's rule
Every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and electrons in single occupied orbitals
What are valance electrons?
The # of valance electrons equal to the atoms main group number
name the four sublevels and the number of orbitals associated with each
S- 1 orbital
P- 3 orbitals
D- 5 orbitals
F- 7 orbitals
What is the significance of valance electrons?
they govern that atom's electronegativity electron affinity, andionization energy, which leads to things such as covalent and ionic bonds
What does it mean when the arrows are drawn facing opposite directions?
a reversible reaction when the reaction when the reaction is at equilibrium
what is ion?
an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons
State the Octet Rule
Atoms tend to from compounds in ways that give them 8 valance electrons, and thus the electron configuration of noble gas
What does the ionization energy value represent?
The energy required to remove the outermost, or least bound, electron from a neutral atom of the element.
Because the atoms gain protons from left to right on the periodic table, what happens to the atomic radius
the atomic radius decreases
How do you determine if an element is a metal or nonmetal?
Metals zre located on the left of the periodic table, and nonmetals are located on the upper right
Explain the concept of a covalent bond
Formed by the equal sharing of electrons from both participating atoms
what is the difference between mass and weight?
One is fundamental measurement of how much matter an object contains. and the other is a measurement of the gravitational force on an object
Explain the difference between accuracy and precision.
One refers to how close a measurement is to the true pr accpeted value. The other refers to how close measurements of the same item are to each other
what is the significance of an elements atomic number
# of protons in the nucleus of each atom of that element
what is an isotope
atoms with the same # of protons but different numbers of neutrons
what is the significance of the atomic orbital (Electron cloud)?
they determine the distribution of electrons in molecules, which in turn determines the elctronic and optical properties of materials
using the periodic table provided to you, tell me all you know about the element pb
soft, silvery white or greyish metal in group 14 (IVa). Lead is very malleable, ductile, and dense and is a poor conducter of electricity.