Unit B Section 2.3 Flashcards
What is a period?
Each horizontal row is called a period (numbered from 1 to 7
What is a group or a family?
Each vertical column forms a group, or family, of elements (numbered from 1 to 18)
Why are some symbols have the first letter of their elements?
Some elements’ symbols were based on Latin names for the elements
Some elements are named after the places they have been discovered in
Some are named after the scientist that discovered them
What is an atomic number?
The number above the element’s symbol on the left is the atomic number
It shows how many protons are in the nucleus of ONE ATOM of the element
Because atoms are neutral, the number of protons
equals the number of electrons.
What is the pattern in the atomic number
the atomic number increases by one for each element as you read across the periodic table from left to right.
What is atomic mass?
The number below the element’s name is the atomic mass.
The atomic mass tells you the total mass of all the protons and neutrons in an atom. (Electrons are so tiny that they have very little effect on the total mass of
the atom.)
Recall that this is the average mass of the element’s atoms. Not all atoms in an element have exactly the same mass
is measured by atomic mass unit (amu).
One amu is defined as 1/12th the mass of a carbon-12 atom
What is mass number?
It represents the sum of the number of protons and neutrons in an atom.
For example, the most common form of carbon atom has six protons and six neutrons. Its mass number is therefore equal to 12
How are mass number and atomic mass different?
The mass number is the sum of the number of protons and neutrons in an atom.
The atomic mass is the average number of protons and neutrons for all-natural isotopes of an element
The majority of the periodic table is green
They are metals.
Metals are shiny, malleable, and ductile. They also conduct electricity.
The second majority of the periodic table that is orange
Non-metals
Non-metals can be a solid or a gas
Solid nonmetals are dull, brittle elements. Non-metals, except carbon, do not conduct electricity.
they are called insulators
The minority part of the periodic table is purple:
metalloids
Metalloids have both metallic and non-metallic properties.
Groups in Periodic table:
The 18 columns in the table contain groups or families of elements with similar chemical properties.
usually referred to by the first element in the column.
-For example, group 10 is the nickel group of elements because nickel is the first element at the top of that column
Group 1 is divided into two parts—hydrogen and the alkali
Hydrogen is considered to be a unique element, and
in some periodic tables, it is placed in a separate spot
Periods in the Periodic table:
The rows in the periodic table, called periods, are numbered 1 to 7.
As you move from left to right across a period, you will notice that the properties of the elements change
From left to right, the elements gradually change from metals to nonmetals.
. The most reactive metals start on the left. As you move right, the metals generally become less reactive.
What are “alkali metals”
Group 1 elements, not including hydrogen, are called alkali metals.
- These are the most reactive of the metals. They react when exposed to air or water.
- As you move down the group, starting with lithium, the reactivity increases
What are alkaline-earth metals
. Group 2 elements are called the alkaline-earth
metals
-They react when exposed to air and water as well, but their reactivity is not as strong as that of the alkali metals.
