Chemistry Chapter 4

What is Dalton's Atomic Theory?

All matter is made of atoms.

Atoms of the same element are identical; atoms of different elements are different.

Atoms combine in whole-number ratios to form compounds, and they cannot be created or destroyed in chemical reactions.

Describe J.J. Thomson's model of the atom and his discovery.

He discovered the electron and proposed the 'plum pudding' model, where electrons are scattered in a positively charged sphere.

Explain Rutherford's Gold Foil Experiment and what it revealed about atomic structure.

It showed that atoms are mostly empty space with a small, dense, positively charged nucleus, as most alpha particles passed through the foil while some bounced back.

atom

the smallest unit of matter that keeps an element's properties.

define element

An element is made up of only one kind of atom.

How are elements and atoms related?

They are related because elements are defined by the type of atoms they contain.

Who arranged the first periodic table and how?

Mendeleev arranged elements by increasing atomic mass and similar properties.

What did Mosley contribute to the periodic table?

He rearranged the periodic table by atomic number, leading to the modern periodic table.

How do we know that matter has charges?

Experiments show that matter can attract or repel, indicating the presence of positive and negative charges.

How do atoms differ from one another?

Atoms differ by the number of protons in their nuclei, which is known as the atomic number.

What does the atomic number represent?

The atomic number represents the number of protons in an atom.

What does the element symbol represent?

represents abbreviation of the element

What is the mass number or atomic mass?

It represents the total number of protons and neutrons in an atom.

What is the element name?

represents element's full name

What are the origins of element names and symbols

Element names come from Latin, Greek, scientists, or locations.

What is Mendeleev's Periodic Law? How did this lead to modern day organization of the periodic table?

It states that when elements are arranged by atomic mass, there are repeating (periodic) patterns in their properties. This led to the modern table, now arranged by atomic number.

What are the general properties of metals?

Metals are shiny, conduct electricity, are malleable, and are solid at room temperature.

What are the properties of nonmetals?

Nonmetals are dull, brittle, poor conductors, and many are gases.

What are the properties of metalloids?

Metalloids have properties of both metals and nonmetals and are semiconductors.

What are the properties of alkali metals?

Alkali metals (Group 1) are very reactive, soft metals with 1 valence electron.

What are the properties of alkaline earth metals?

Alkaline earth metals (Group 2) are reactive and have 2 valence electrons.

What are the properties of halogens?

Halogens (Group 17) are very reactive nonmetals with 7 valence electrons.

What are the properties of noble gases?

Noble gases (Group 18) are unreactive and have a full outer shell.

What is an ion?

An ion is an atom that has gained or lost electrons, resulting in a negative ion (anion) or a positive ion (cation).

What are isotopes?

Isotopes are atoms of the same element with different numbers of neutrons.

example of an isotope:

Carbon-14.

¹⁴₆C. (mass number over atomic number)

Explain how average atomic mass is calculated from isotopes.

Average atomic mass is calculated as a weighted average of all isotopes based on their natural abundance.

Describe radioactive isotopes, how they are used, and their benefits.

Radioactive isotopes are unstable isotopes that decay over time, releasing radiation and are used in medicine, archaeology, and power generation.

How do we know that all matter is made of atoms?

Microscopes and experiments show matter is made of tiny particles (atoms).

What evidence supported the existence of a nucleus?

Rutherford's gold foil experiment showed particles bouncing off a dense center.

Which subatomic particle determines an atom's identity?

Proton

How can you find an element's atomic number?

It's listed above the element symbol on the periodic table (equals protons)

What patterns exist in the main groups?

Elements in the same group share valence electrons and similar reactivity.

What is charge of 11 protons and 10 electrons?

+1 charge (Na⁺)

How do you find electrons in a 2+ cation?

Subtract 2 from number of protons

What does carbon-14 represent?

Carbon atom with 6 protons and 8 neutrons.

How many neutrons are in chlorine-37?

20 neutrons.

(37 - 17 = 20)