Basics of Matter Flashcards
What is radioactive decay?
Most isotopes radioactively decay back into their “normal” forms over time. The time required for half the atoms of a particular substance to disintegrate is known as that substance’s half life.
What is a substance’s “half life”?
The time required for half the atomas of a particular substance to disintegrate (during radioactive decay) is known as that substance’s half life
Ex: Carbon 14/isotope- it decreases by half each 5400 years. Keeps decreasing by half so the overall amount (and the amount it decays) keeps decreasing.
What is Carbon 14?
a very special isotope create in the earth’s atmosphere by cosmic rays (it can be used to date when a living thing died.)
All living things absorb Carbon 14 when they respirate (even plants).
When they die, this absorption stops, and the organism’s existing C14 begins to radioactively decay back into C12. SO we observe how long it has been taking place that its been decaying back, so we know how long the decay has been taking place.
Ex: looking at the rings of trees, looking at how much less carbon 14 than carbon 12. Can do it with a human body. Measures how long the thing died.
What is a limitation about Carbon 14?
Because of the specific half life of C14, radiocarbon dating only works on organisms that died less than 50,000 years ago.
Besides Carbon 14, how else can you use to tell how long things have been dead?
- many elements have much longer lives than C14, and can be used to date non-living things.
- ex: MOON rocks, which are millions of years old
How to read Periodic table- Two general rules.
- Atomic properties are organized by ROW. Atomic number and mass increase as you move left to right and top to bottom, like reading a book. (Atomic # and atomic mass. The bottom right has the most mass.)
- Chemical properties are loosely arranged by COLUMN. (Behave the same way within noble gases, want to bond with each other. Same with metals, etc. Organize by properties, how they are going to behave. Alkali metals, Earth metals, transitional metals, noble gases, etc. **each column has the number of electrons in their outermost shell.
How do you look for the answer if they ask what element is similar in terms of chemical property?
choose the one in the same column, same color Ex: Na and K (Sodium and Postassium)
How do you find an element on the periodic table when they ask to mach similar/same atomic numbers and/or mass?
you match the numbers- mg (12) Na1 (11) same ROWWWW
What is a compound?
a substance composed of two or more elements
ex: H20, NaCL, Co2, etc.
What are bonds?
Within compounds (two or more elements together), the various atoms making up molecules are held together by bonds.
What are two important types of bonds to know? (they are both strong-force bonds)
- Ionic
2. Covalent
What is an Ionic bond?
A bond in which one atom LOSES an electron to form a positive ion and other gains an electron to form a negative ion, creating an electrostatic force which holds them together.
Ex: Think of one child playing with a ball and the other steals it. The first child wants it back so he chases the second child around to try and get it. The chase is the electrostatic force that holds them together (the ions)
What is a Covalent bond?
A bond formed when atoms share one or more of their valence electrons. Ex: One child has the ball, the other TRIES to steal but they won’t let go, both held together.
