chem 121 ch 2
he sum of the numbers of protons and neutrons in a nucleus is called
mass number
In a neutral atom the number of ________ is equal to the number of _____.
protons, electrons
Electrons are grouped into general regions called
shells
four types of subshells, and each type can hold up to a maximum number of electrons
subshells
electron configuration of an atom
the distribution of electrons into shells and subshells is the
electrically neutral atom
the number of protons equals the number of electrons.
The electron was the first subatomic particle to be discovered, and has a mass of 9.109 × 10-31 kg.
true
A nonmetal
typically dull and a poor conductor of electricity and heat. Solid nonmetals are also very brittle
How many electrons are present in a neutral atom of carbon? (Hint: The atomic number of carbon is 6.)
6
An atom containing 29 protons, 29 electrons, and 34 neutrons has a mass number of
63. protons + neutrons
Which element is most likely to have chemical properties similar to those of bromine (atomic number 35)?
I (atomic number 53)
Mendeleev
he made some bold predictions regarding the properties of those undiscovered elements. organized all the known elements according to similar properties.
Which of is the most abundant element in the universe ?
hydrogen
elements that exist as diatomic molecules
hydrogen (H2), oxygen (O2), nitrogen (N2), fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2).
A metal
is shiny, typically (but not always) silvery in color, and an excellent conductor of electricity and heat. Metals are also malleable (they can be beaten into thin sheets) and ductile (they can be drawn into thin wires).
An element may have different numbers of neutrons in the nuclei of its atoms; such atoms are referred
isotopes
naturally occurring elements
90
The electronic configuration of silicon is 1s22s22p63s22p2.
true
Which of the following statements is true of 56 26 FE?
26 is the number of protons in iron
chemical symbol.
Each element has a one- or two-letter
How many electrons can occupy the shell having n = 4?
32
An s-block element in the 5th Period is
Sr
horizontal row of elements is called
period
The word halogen comes from the Greek for
"salt maker" because these elements combine with other elements to form a group of compounds called salts.
Radon
1) an invisible, odorless noble gas from the ground, 2) from rocks and soils whose uranium content is high. 3) it is a noble gas, radon is not chemically reactive. 4) it is radioactive, and increased exposure to it has been correlated with an increased lung cancer risk.
What is the number of protons in the nucleus of each element? 1. aluminum
1. According to the table, aluminum has an atomic number of 13. Therefore, every aluminum atom has 13 protons in its nucleus.
How many electrons are present in the atoms of each element? 1. sulfur
1. The atomic number of sulfur is 16. Therefore, in a neutral atom of sulfur, there are 16 electrons.
How many protons and neutrons are in each atom? MASS #>35 ATOMIC #>17 Cl
17 protons, and 35 − 17 = 18 neutrons in each nucleus.
What is an atomic mass unit?
An atomic mass unit is 1/12th of the mass of a 12C atom. It is equal to 1.661 × 10−24 g.
quantum mechanics
The modern theory of electron behavior
Dalton
a modern atomic theory,
Looking at the periodic table, where do the following elements appear? a. the metals b. the nonmetals c. the halogens d. the transition metals
a. the left three-quarters of the periodic table b. the right quarter of the periodic table c. the next-to-last column of the periodic table d. the middle section of the periodic table
Which characteristics correctly describe an electron?
approximate mass 5 x 10^-4 amu; charge -1; outside nucleus
number of protons is
atomic number of the element.
Rutherford's experiments showed some alpha particles that were deflected straight back, indicating that electrons were concentrated in the nucleus.
false
There are 90 man made elements known today.
false
Vertical columns of elements
families main group elements, transition metals, lanthanide elements, and actinide elements
