topic 1 - atomic structure + periodic table Flashcards
Describe the structure of an atom
a nucleus containing protons and neutrons, surrounded by electrons in shells
Relative charges of subatomic particles
Protons: +1
Neutrons: 0
Electrons: -1
Relative mass of subatomic particles
Protons: 1
Neutrons: 1
Electrons: 0.0005
Why do atoms contain an equal number of protons and electrons
The + and - charges cancel each other out, making it stable
Describe the nucleus of an atom
very small compared to the overall size of the atom (most of an atom is empty space)
Where is most of the mass of an atom concentrated?
Nucleus
What does an atoms mass number mean?
Total number of protons and neutrons in it’s nucleus
Describe atoms of a given element
They have the same number of protons in the nucleus and this number is unique to each element
What are isotopes?
An element that has the same number of protons but a different number of neutrons
How do you calculate the numbers of protons, neutrons and electrons in atoms given the atomic number and mass number
Atomic number: number of protons (=number of electrons)
Atomic mass: number of protons and neutrons in an atom
What is the result of an isotope’s existence?
The RAM of some elements are not whole numbers
What is RAM
The average of the mass numbers of different isotopes, weighted by how common each isotope is
How to calculate the RAM of an element?
RAM = ((% of isotope a x mass of isotope a) + (% of isotope b x mass of isotope b)) / 100
How did Mendeleev arrange the elements?
In a periodic table by atomic mass and similar chemical properties
What could Mendeleev predict?
He used the periodic table to predict the existence and properties of elements not yet discovered
Why was some of Mendeleev’s table inaccurate?
He believed the elements were ordered in increasing RAM but this wasn’t always true due to the existence of isotopes
What does an element’s atomic number tell us about it?
Tells us how many protons are in its nucleus and where it sits in the periodic table
How are elements arranged in the groups and periods of the periodic table?
- By increasing atomic number
- Groups: similar chemical properties
- Periods: same number of electron shells
What does an elements position in the periodic table tell us about its electronic configuration?
Group number = electrons in outer shell
Period number = number of electron shells
Identify elements as metals or non-metals according to their position in the periodic table
Metals: mostly left/centre of table, because metals only have few electrons in their outer shell
Non-metals: right side of table, have more electrons in outer shell
How are cations formed?
Metals lose electrons to form positively charged ions (cations)
How are anions formed?
Non-metals gain electrons to form negatively charged ions (anions)
What do the dots and crosses represent in dots and cross diagrams?
Dots: non-metals
Crosses: metals
What is an ion?
Charged particles made when electrons are transferred
