25 Sem 1 Flashcards
(37 cards)
What is an element?
A pure substance made of only one type of atom.
What is a compound?
A substance made of two or more atoms chemically bonded.
What are the 3 parts of an atom?
Protons (+), Neutrons (0), Electrons (–).
Where are protons and neutrons found?
In the nucleus.
What does the atomic number tell you?
The number of protons (and electrons in a neutral atom).
What is the mass number?
The total number of protons and neutrons.
What is a valence electron?
An electron in the outermost shell.
What is the electron configuration rule?
2, 8, 8, 2.
What is an ion?
An atom that has gained or lost electrons to become charged.
Why do ions form?
To get a full outer shell.
What do groups show?
Number of valence electrons.
What do periods show?
Number of electron shells.
Where are metals found on the table?
On the left and middle.
What group are the noble gases?
Group 18.
Which group is the most reactive metal group?
Group 1 – Alkali metals.
What is an isotope?
Atoms of the same element with different numbers of neutrons.
What is a radioisotope?
An unstable isotope that emits radiation.
Why is the atomic mass a decimal?
It’s an average of all isotopes.
What is half-life?
The time it takes for half a radioactive substance to decay.
Name the 3 types of radiation.
Alpha, Beta, Gamma.
What stops alpha particles?
Paper or skin.
What is one medical use of radiation?
Radiotherapy to treat cancer.
What does the particle theory say?
All matter is made of particles in constant motion.
What is density?
Mass ÷ Volume (how tightly packed particles are).
