atoms and the periodic table

Suppose that you have just discovered a new element and have it named neptunite. While studying your new element, you find that it has two isotopes— neptunite-220 and neptunite-250. What is the average atomic mass of your new element? (assume that these two isotopes are present in equal amounts in nature.)

235 amu

The atomic mass of an element is...

A weighted average of the masses of an elements isotopes

why is Bohrs model of the Adam often called the planetary model?

Bohr's atomic model represents electrons as moving in fixed orbits around the nucleus like planets moving in orbit around the sun

what did Bohr's model of the atom do that Rutherford's model did not?

Bohr's model focused on electrons

A particle that moves around the nucleus is a(n) [blank]

Electron

How was Bohr's atomic model similar to Rutherford's model?

It described a nucleus surrounded by a large volume of space.

elements that are gases, or brittle, and are poor conductors at room temperature are...[blank]

Nonmetals

which of the following most accurately represents John Dalton's model of the atom?

a tiny, solid sphere with a predictable mass for a given element

what did the the greek philosopher democritus coined what word for any tiny piece of matter that cannot be defined?

atom

The number of protons one Adam of an element is that elements...

atomic number

moving from left to right across a row of the periodic table, which of the following values increases by EXACTLY one from element to element.

atomic number

to find the number of neutrons in and atom, he would subtract...

atomic number for mass number

which of the following is NOT a part of John Dalton's atomic theory?

atoms contain subatomic particles

and in atomic model that includes the nucleus, positive charge is...

concentrated in the center of atom.

JJ Thompson's experiments provided evidence that atom...?

contains negatively charged particles

Which subatomic particle has a negative charge?

electron

who provided evidence for the existence of a nucleus in an atom?

ernest rutherford

A certain atom has 26 protons, 26 electrons, and 30 neutrons. It's mass number is...[blank]

fifty-six

how does the electron cloud model of the atom represent the locations of electrons in atoms?

it provides a visual model of the most likely locations of electrons in an atom

in Niels Bohr's model of the atom electrons move...

like planets orbiting the sun

mendeleev arranged the known chemical elements in a table according to increasing...

mass

The glowing of a neon light is caused by electrons emitting energy as they...

move from higher to lower energy levels

in figure 4-2, what is the main difference between the atomic model in panel one and in the model in panel two?

panel one depicts an atom as a solid sphere without any subatomic particles. panel two shows that an atom has a subatomic structure.

What do scientists used to predict the locations of electrons in atoms?

probability

In a periodic table, a set of properties repeats from...

row to row

how did the results of JJ Thomson's experiments change how scientists thought about atoms?

scientists realized that atoms contain smaller subatomic particles

democritus thought that matter was made of tiny particles...

that could not be divided.

in figure 4-2, what is the main difference between the atomic model in panel two and the model in panel three

the main difference is the way in each electron motion is depicted. in panel two, the movement of electrons is represented by fixed circular orbits. and in panel three, the probable locations of the moving electrons is represented by a cloud

Which of the following is unique for any given element?

the number of protons

according to John Dalton's observation, when elements combine in a compound...

the ratio of their masses is always the same

read the following analogy and explain how it applies to panels one and two, in figure 4-2: "the atomic model and panel one is to the model and panel two as a drawing of the outside of a house is to a blueprint of the inside."

the solid ball in panel one is like the drawing of the exterior of the house. He provides no details about the internal structure of an atom. The model in panel two shows the locations of different parts of the atom within the atom in the relative sizes. It is like a blueprint that shows the size and location of rooms in the house

why did Rutherford propose a new model of the atom after seeing results of the gold foil experiment?

thomson's model no longer explained all the available evidence. in Thomson's model, for example, positive charges spread evenly throughout the atom. Rutherford had concluded that the positive charge of an atom was concentrated in the center of the atom

are the atomic models in figure 4-2 arranged in the order they were developed? explain your answer.

yes; they go from the simplest (the solid sphere in one close parentheses to the most complex (the electron cloud diagram and panel three).