Unit 1: Intro Chem
What is the study of the composition of matter and the changes that matter undergoes?
chemistry
The sum of the protons and neutrons in an atom equals the ____.
atomic mass number
The Greek philosopher Democritus was the first to propose the idea that matter was composed of small units called what?
Which scientist is known as the "father of the periodic table" and accurately predicted the properties of undiscovered elements?
Dmitri Mendeleev
Which is formed when an atom loses an electron and becomes positively charged?
cation
Which is an example of an extensive property?
Mass, volume, weight
How many significant figures are in the number 0.00208?
3
What is the current model of the atom that estimates the probability of finding an electron in a certain position?
Quantum mechanical model
What is the definition of electronegativity?
attract electrons
How many valence electrons are in an atom of phosphorus (group 5A), and what is its ion charge?
5 and -3
Which is an example of a chemical change?
Burnt toast, burning anything, baking soda and vinegar, baking
Avogadro's number of representative particles (6.02x1023) is equal to one ____.
mole
What are three parts of an atom and their charges?
proton +
electron -
neuron 0
Which group is made up of nonreactive gases?
noble gases
What is the formula for dinitrogen pentoxide?
N2O5
Give an example of a homogeneous and a heterogeneous mixture
jello
and
salad
What type of reaction is 2 Mg + O2 → 2 MgO?
synthesis
An element has an atomic number of 9 and an atomic mass of 19. How many protons and neutrons are in this element?
9 protons and 10 neutrons
Which of the following elements has the lowest ionization energy?
A) sulfur
B) selenium
C) chlorine
D) bromine
selenium
What is the name for KBr?
potassium bromide
What are the steps of the scientific method?
make observations
ask questions
form a hypothesis
perform an experiment
collect data
draw conclusions
How do you convert from mass (grams) to moles?
Example: how many moles are in 2 grams of hydrogen?
Divide by the molar mass
Why are Carbon-12 and Carbon-14 considered isotopes?
they have different number of neutrons
Which element is the most electronegative?
What is a valence electron?
The total number of electrons in the outermost energy level