A radioactive element is an element which is subject to spontaneous degeneration of its nucleus followed by the emission of alpha, beta and gamma particles. All elements with atomic numbers greater than 83 are radioactive.
The given phrases that describe radioactive elements are-
They have a consistent number of particles
- the particles are alpha, beta and gamma particles.
They have a half-life that determines their rate of decay.
Explanation for other options:
Not all elements occur in nature. Radioactive decay rates may not be constant as the decay happens when a radioactive substance emits a particle. It is not possible to predict exactly when a given atom of a substance will emit a particular particle. When the radioactive element release energy and particles, it decays.
Answer:
a. A hypothesis that does not generate a testable prediction is not useful.
Explanation:
In the scientific method, we generate a hypothesis to explain a phenomenon. After this, it is necessary to create a method to test the hypothesis and make predictions. Moving forward, we test this methodology, generating results and reject or not reject the hypothesis. If the hypothesis can't be tested, the scientific method can't be applied.
.Oxygen free environments
.Concentrated salt water and hot
. Acidic water of sulfur springs
Answer:
Meiosis
Explanation:
Because it forms 4 daughter cells which are haploid (half the amount of chromosomes as parent cell )
This is true , trees loose their leaves as a part of growth, also in seasons they loose leaves.
