Chemistry Exam 2 Practice

What is the mass number of an ion with 105 electrons, 157 neutrons, and a 1+ charge?

263

About how many different kinds of atoms (elements)are found in nature?

91

What is the mass number of an isotope?

The mass number of an isotope is the sum of the number of protons and the number of neutrons found in the nucleus of the particular isotope.

An element is defined by what?

The number of protons

What is the percent natural abundance of isotopes?

The percent natural abundance of isotopes provides the relative amounts of each isotope found in a sample of the element. For a given element, the relative amounts of each different isotope in a naturally occurring sample of that element are always the same.

True or False: Electrons are negatively charged particles?

True

What scientist formalized a theory of the atom that gained broad acceptance?

Dalton

Rutherford's Nuclear Atom Model

A positive charge is condensed in one location within the atom. The majority of the space inside the atom is empty space. The atom contains a positively charged nucleus.

Dalton's Atomic Theory

All matter is made of atoms which are indivisible and indestructible. All atoms of a given element are identical in mass and properties. Compounds are formed by a combination of two or more different kinds of atoms. A chemical reaction is a rearrangement of atoms.

Rutherford performed the gold foil experiment to what?

Confirm the plum pudding model

What is electrical charge?

Electrical charge is a fundamental property of the proton (positive charge) and the electron (negative charge). The positive charge is attracted to the negative charge while is is repelled by another positive charge, and vice versa. When the number of protons is equal to the number of electrons, the charges are effectively cancelled and the molecule is neutral in charge.

True Statements about Electrons

Electrons are lighter than neutrons. Electrons are attracted to protons and electrons repel each other.

Prediction of the Structure of the Atom

In an atom, negatively charged electrons are dispersed in the space surrounding the positively charged nucleus of an atom. In an atom, most of the mass and the positive charge are located in a small core within the atom called the nucleus.

Which term represents the sum of protons and neutrons?

Mass number

What scientist noticed that certain groups of elements had similar properties?

Mendeleev

What elements are located on the left side of the periodic table?

Metals

Work done after Rutherford's gold foil experiment demonstrated that the nucleus contained what?

Protons and Neutrons

Describe Rutherford's gold foil experiment and the results of that experiment.

Rutherford had shot alpha particles at an extremely thin gold foil target. The majority of alpha particles passed directly through the foil, some particles were slightly deflected and 1 in 20,000 bounced back toward the alpha source.

Magnesium has significantly fewer protons and neutrons than gold. If you were to use Mg in place of Au in the Rutherford experiment, how would you predict the results from the experiment to change?

The center spot would be smaller and the alpha particle scattering would be reduced.

How do the results of the Rutherford experiment suggest that the nucleus is positively charged?

The large center spot is caused by small alpha particle deflections when they pass by a positively charged nucleus.

True or False: Positive and negative charges attract

True