Chemistry Test Flashcards
Substances can be classified into what two categories?
Elements and compounds
What is a substance that can’t be broken down into simpler substances
An element
What is the smallest particle of an element
An atom
Why does an atom have a fixed composition
Because it contain only one type of element
What is a substance that is made from two or more simpler substances and can be broken down into those simpler substances
A compound
What does a compound always contains
Two or more elements joined at fixed proportion
What is any ability to produce a change in the composition of matter
A chemical property
What can only be observed when the substances in a sample of matter are changing in different substances
Chemical properties
What is a materials ability to burn in the presence of oxygen
Flammability
What is the property that describes how readily a substance combines chemically with another substance
Reactivity
What occurs when a substance reacts and forms one or more new substances
A chemical change
What are the three common types of evidence for a chemical change
Change in color, production of gas, and the formation of a precipitate,
What is any solid that forms a liquid mixture called
A precipitate
What is the difference between a chemical change and a physical change
Chemical change: changes composition of matter
Physical change: composition of matter stays the same
What is a dense positively charged center of the Atom
The nucleus
What are the subatomic particles
Protons, electrons, neutrons
What is a positively charged subatomic particle found in the nucleus of an Atom
Proton
What is a negatively charged subatomic particle found outside nucleus of an atom
Electron
What is a neutral subatomic particle that is found in the nucleus
Neutron
Matter that always has exactly the same composition is classified as a what?
A pure substance
Protons electrons and neutrons can be distinguished by what
Mass, charge, and location in Atom
What of elements equals the number of protons in an atom of that element
Atomic number
Atoms of different elements have different numbers of what
Protons
What is the sum of protons and neutrons in the nucleus in an Atom
The mass number
The possible energies that electrons in an Atom can have Are called what
Energy levels
What’s in a Atom can move from one energy level to another when the atom gains or loses energy
An electron
What is a visual model of the most likely locations for electrons and Atom
Electron cloud
Scientists use what to describe the possible locations of electrons around the nucleus
An electron cloud model
What is a region of space around the nucleus were an electron is most likely to be found
An orbital
What is a good approximation of how electrons behave in the orbitals
An electron cloud
What is the arrangement of electrons in the orbitals of an Atom
An electron configuration
What is the most stable electron configuration
When electrons are in their orbitals with the lowest possible energies
What is it called when all the electrons in and atom have the lowest possible energies
Ground state
What is an arrangement of elements in column based on a set of properties that repeat from Row to row
A periodic table
What are the elements arranged by in the modern periodic table
Atomic number
What is a value that depends on the distribution of elements isotopes in nature and the masses of those isotopes
Atomic mass
What is defined as one twelfth the mass of a Carbon – 12 Atom
Atomic mass unit
What are elements classified as
Metals, nonmetals, metalloids
What are elements that are good conductors of electric current and heat
Metals
What are elements that form a bridge between the elements on the left and right sides of the table
Transition metals
What are elements that are poor conductors of heat and electric current
Nonmetals
What are elements with properties that fall between those of metals and nonmetals
Metalloids
Across a period from left to right do elements become more nonmetallic or more metallic in their properties
More nonmetallic
What is an electron that is in the highest occupied energy level of an Atom
A valence electron
Why do elements in a group have similar properties
Because they have the same number of valence electrons
What are elements in group 1A called
Alkali metals
The reactivity of alkali metals increases from the top of group 1A bottom or bottom to top
Top to bottom
What are elements in group 2A called
Alkaline earth metals
How are differences in the reactivity among alkaline earth metals shown
By the way they react to water
The elements in group 8A are called what
Noble gases
What are colorless and odorless and extremely unreactive
The noble gases
