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