.whatsapp_button {
    position: fixed;
    background-color:#00bb2d;
    width: 4em;
    height: 4em;
    border-radius:50%;
    bottom: 1em;
    left: 1em;
    z-index: 100;
    display: flex;
    justify-content: center;
    align-items: center;
    color: white;
    box-shadow: 0px 0px 5px 0px rgba(112,112,112,1);
}

.whatsapp_button i {
    font-size: 2.5em;
}